diff --git a/pykd/customtypes.cpp b/pykd/customtypes.cpp
new file mode 100644
index 0000000..9ae22ac
--- /dev/null
+++ b/pykd/customtypes.cpp
@@ -0,0 +1,98 @@
+
+#include "stdafx.h"
+#include "customtypes.h"
+
+////////////////////////////////////////////////////////////////////////////////
+
+namespace pykd {
+
+////////////////////////////////////////////////////////////////////////////////
+
+TypeInfoPtr CustomStruct::create(const std::string &name, ULONG alignReq /*= 0*/)
+{
+    return TypeInfoPtr( new CustomStruct(name, alignReq) );
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+ULONG CustomStruct::getSize()
+{
+    if (UdtFieldColl::empty())
+        return 0;
+
+    UdtUtils::Field &field = UdtFieldColl::last();
+    return field.m_offset + field.m_type->getSize();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+void CustomStruct::appendField(const std::string &fieldName, TypeInfoPtr fieldType)
+{
+    bool fieldExist = false;
+    try
+    {
+        lookupField(fieldName);
+        fieldExist = true;
+    }
+    catch (const TypeException &except)
+    {
+        DBG_UNREFERENCED_PARAMETER(except);
+    }
+    if (fieldExist)
+        throw TypeException(getName(), "duplicate field name: " + fieldName);
+
+    ULONG offset = getSize();
+    offset += (offset % m_alignReq);
+    UdtFieldColl::push_back(
+        UdtUtils::Field(offset, fieldName, fieldType)
+    );
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+TypeInfoPtr CustomUnion::create(const std::string &name)
+{
+    return TypeInfoPtr( new CustomUnion(name) );
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+ULONG CustomUnion::getSize()
+{
+    ULONG size = 0;
+    for (ULONG i = 0; i < getFieldCount(); ++i)
+    {
+        ULONG fieldSize = lookupField(i).m_type->getSize();
+        if (fieldSize > size)
+            size = fieldSize;
+    }
+    return size;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+void CustomUnion::appendField(const std::string &fieldName, TypeInfoPtr fieldType)
+{
+    bool fieldExist = false;
+    try
+    {
+        lookupField(fieldName);
+        fieldExist = true;
+    }
+    catch (const TypeException &except)
+    {
+        DBG_UNREFERENCED_PARAMETER(except);
+    }
+    if (fieldExist)
+        throw TypeException(getName(), "duplicate field name: " + fieldName);
+
+    UdtFieldColl::push_back(
+        UdtUtils::Field(0, fieldName, fieldType)
+    );
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+}   // namespace pykd
+
+////////////////////////////////////////////////////////////////////////////////
diff --git a/pykd/customtypes.h b/pykd/customtypes.h
new file mode 100644
index 0000000..199f559
--- /dev/null
+++ b/pykd/customtypes.h
@@ -0,0 +1,69 @@
+
+#pragma once
+
+////////////////////////////////////////////////////////////////////////////////
+
+#include "typeinfo.h"
+#include "win\dbgeng.h"
+
+////////////////////////////////////////////////////////////////////////////////
+
+namespace pykd {
+
+////////////////////////////////////////////////////////////////////////////////
+
+class CustomStruct : public UdtFieldColl
+{
+public:
+    static TypeInfoPtr create(const std::string &name, ULONG alignReq = 0);
+
+protected:
+    CustomStruct(const std::string &name, ULONG alignReq)
+        : UdtFieldColl(name), m_name(name), m_alignReq(alignReq ? alignReq : ptrSize()) 
+    {
+    }
+
+    virtual std::string getName() override {
+        return m_name;
+    }
+
+    virtual ULONG getSize() override;
+
+    virtual void appendField(const std::string &fieldName, TypeInfoPtr fieldType) override;
+
+    virtual std::string getTypeString() const override {
+        return "custom struct";
+    }
+
+private:
+    std::string m_name;
+    ULONG m_alignReq;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+class CustomUnion : public UdtFieldColl
+{
+public:
+    static TypeInfoPtr create(const std::string &name);
+
+protected:
+    CustomUnion(const std::string &name) : UdtFieldColl(name) {}
+
+    virtual ULONG getSize() override;
+
+    virtual void appendField(const std::string &fieldName, TypeInfoPtr fieldType) override;
+
+    virtual std::string getTypeString() const override {
+        return "custom union";
+    }
+
+private:
+    std::string m_name;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+}   // namespace pykd
+
+////////////////////////////////////////////////////////////////////////////////
diff --git a/pykd/pykd_2008.vcproj b/pykd/pykd_2008.vcproj
index 24fdecb..b9f14b2 100644
--- a/pykd/pykd_2008.vcproj
+++ b/pykd/pykd_2008.vcproj
@@ -361,6 +361,10 @@
 				RelativePath=".\cpureg.cpp"
 				>
 			</File>
+			<File
+				RelativePath=".\customtypes.cpp"
+				>
+			</File>
 			<File
 				RelativePath=".\dbgexcept.cpp"
 				>
@@ -467,6 +471,10 @@
 				RelativePath=".\cpureg.h"
 				>
 			</File>
+			<File
+				RelativePath=".\customtypes.h"
+				>
+			</File>
 			<File
 				RelativePath=".\dbgengine.h"
 				>
diff --git a/pykd/pymod.cpp b/pykd/pymod.cpp
index b2e8fad..d43e39b 100644
--- a/pykd/pymod.cpp
+++ b/pykd/pymod.cpp
@@ -14,6 +14,7 @@
 #include "dbgexcept.h"
 #include "dbgmem.h"
 #include "typeinfo.h"
+#include "customtypes.h"
 #include "typedvar.h"
 #include "cpureg.h"
 #include "disasm.h"
@@ -59,6 +60,8 @@ BOOST_PYTHON_FUNCTION_OVERLOADS( getSourceFile_, getSourceFile, 0, 1 );
 BOOST_PYTHON_FUNCTION_OVERLOADS( setSoftwareBp_, setSoftwareBp, 1, 2 );
 BOOST_PYTHON_FUNCTION_OVERLOADS( setHardwareBp_, setHardwareBp, 3, 4 );
 
+BOOST_PYTHON_FUNCTION_OVERLOADS( CustomStruct_create, CustomStruct::create, 1, 2 );
+
 BOOST_PYTHON_MODULE( pykd )
 {
     python::scope().attr("version") = pykdVersion;
@@ -231,6 +234,12 @@ BOOST_PYTHON_MODULE( pykd )
     python::def( "removeAllBp", &breakPointRemoveAll,
         "Remove all breapoints" );
 
+    // custom types
+    python::def( "createStruct", &CustomStruct::create, CustomStruct_create( python::args( "name", "alignReq" ), 
+        "Create empty structure. Use append() method for building" ) );
+    python::def( "createUnion", &CustomUnion::create,
+        "Create empty union. Use append() method for building" );
+
     python::class_<intBase>( "intBase", "intBase", python::no_init )
         .def( python::init<python::object&>() )
         .def( "__eq__", &intBase::eq )
@@ -334,6 +343,7 @@ BOOST_PYTHON_MODULE( pykd )
         .def( "field", &TypeInfo::getField )
         .def( "asMap", &TypeInfo::asMap )
         .def( "deref", &TypeInfo::deref )
+        .def( "append", &TypeInfo::appendField )
         .def( "__str__", &TypeInfo::print )
         .def( "__getattr__", &TypeInfo::getField )
         .def("__len__", &TypeInfo::getElementCount )
diff --git a/pykd/typeinfo.cpp b/pykd/typeinfo.cpp
index 965e583..95b3544 100644
--- a/pykd/typeinfo.cpp
+++ b/pykd/typeinfo.cpp
@@ -557,10 +557,45 @@ ULONG64 TypeInfo::getStaticOffset()
 
 /////////////////////////////////////////////////////////////////////////////////////
 
-ULONG UdtTypeInfo::getFieldCount()
+std::string UdtFieldColl::print()
 {
-    refreshFields();
-    return (ULONG)m_fields.size();
+    std::stringstream  sstr;
+
+    sstr << getTypeString() << ": " << getName() << " Size: 0x" << std::hex << getSize() << " (" << std::dec << getSize() << ")" << std::endl;
+    
+    ULONG       fieldCount = getFieldCount();
+
+    for ( ULONG i = 0; i < fieldCount; ++i )
+    {
+        const UdtUtils::Field &udtField = lookupField(i);
+        TypeInfoPtr     fieldType = udtField.m_type;
+
+        if ( fieldType->isStaticMember() )
+        {   
+            sstr << "   =" << std::right << std::setw(10) << std::setfill('0') << std::hex << fieldType->getStaticOffset();
+            sstr << " " << std::left << std::setw(18) << std::setfill(' ') << udtField.m_name << ':';
+        }
+        else
+        if ( fieldType->isVirtualMember() )
+        {
+            ULONG virtualBasePtr, virtualDispIndex, virtualDispSize;
+            fieldType->getVirtualDisplacement( virtualBasePtr, virtualDispIndex, virtualDispSize );
+
+            sstr << "   virtual base " <<  fieldType->getVirtualBase()->getName();
+            sstr << " +" << std::right << std::setw(4) << std::setfill('0') << std::hex << udtField.m_offset;
+            sstr << " " << udtField.m_name << ':';
+        }
+        else
+        {
+            sstr << "   +" << std::right << std::setw(4) << std::setfill('0') << std::hex << udtField.m_offset;
+            sstr << " " << std::left << std::setw(24) << std::setfill(' ') << udtField.m_name << ':';
+        }
+
+        sstr << " " << std::left << fieldType->getName();
+        sstr << std::endl;
+    }
+
+    return sstr.str();
 }
 
 /////////////////////////////////////////////////////////////////////////////////////
@@ -615,7 +650,9 @@ void UdtTypeInfo::getFields(
                 break;
             }
 
-            m_fields.push_back( UdtUtils::Field( fieldOffset, childSym->getName(), ti ) );
+            UdtFieldColl::push_back(
+                UdtUtils::Field( fieldOffset, childSym->getName(), ti )
+            );
         }
         else
         if ( symTag == SymTagVTable )
@@ -632,7 +669,7 @@ void UdtTypeInfo::getFields(
                
             }
 
-            m_fields.push_back( 
+            UdtFieldColl::push_back( 
                 UdtUtils::Field( startOffset + childSym->getOffset(), "__VFN_table", ti )
             ); 
         }
@@ -666,7 +703,7 @@ void UdtTypeInfo::getVirtualFields()
 
 void UdtTypeInfo::refreshFields()
 {
-    if ( m_fields.empty() )
+    if ( UdtFieldColl::empty() )
     {
         getFields( m_dia, SymbolPtr() );
         getVirtualFields();
@@ -675,49 +712,6 @@ void UdtTypeInfo::refreshFields()
 
 /////////////////////////////////////////////////////////////////////////////////////
 
-std::string UdtTypeInfo::print()
-{
-    std::stringstream  sstr;
-
-    sstr << "struct/class: " << getName() << " Size: 0x" << std::hex << getSize() << " (" << std::dec << getSize() << ")" << std::endl;
-    
-    ULONG       fieldCount = getFieldCount();
-
-    for ( ULONG i = 0; i < fieldCount; ++i )
-    {
-        const UdtUtils::Field &udtField = lookupField(i);
-        TypeInfoPtr     fieldType = udtField.m_type;
-
-        if ( fieldType->isStaticMember() )
-        {   
-            sstr << "   =" << std::right << std::setw(10) << std::setfill('0') << std::hex << fieldType->getStaticOffset();
-            sstr << " " << std::left << std::setw(18) << std::setfill(' ') << udtField.m_name << ':';
-        }
-        else
-        if ( fieldType->isVirtualMember() )
-        {
-            ULONG virtualBasePtr, virtualDispIndex, virtualDispSize;
-            fieldType->getVirtualDisplacement( virtualBasePtr, virtualDispIndex, virtualDispSize );
-
-            sstr << "   virtual base " <<  fieldType->getVirtualBase()->getName();
-            sstr << " +" << std::right << std::setw(4) << std::setfill('0') << std::hex << udtField.m_offset;
-            sstr << " " << udtField.m_name << ':';
-        }
-        else
-        {
-            sstr << "   +" << std::right << std::setw(4) << std::setfill('0') << std::hex << udtField.m_offset;
-            sstr << " " << std::left << std::setw(24) << std::setfill(' ') << udtField.m_name << ':';
-        }
-
-        sstr << " " << std::left << fieldType->getName();
-        sstr << std::endl;
-    }
-
-    return sstr.str();
-}
-
-/////////////////////////////////////////////////////////////////////////////////////
-
 TypeInfoPtr EnumTypeInfo::getField( const std::string &fieldName )
 {
     return TypeInfo::getTypeInfo( m_dia, fieldName );
diff --git a/pykd/typeinfo.h b/pykd/typeinfo.h
index 9a627eb..d3fe052 100644
--- a/pykd/typeinfo.h
+++ b/pykd/typeinfo.h
@@ -157,6 +157,10 @@ public:
         throw PyException( PyExc_TypeError, "object is unsubscriptable");  
     }
 
+    virtual void appendField(const std::string &fieldName, TypeInfoPtr fieldType) {
+        throw TypeException( getName(), "type is not is not extensible" );
+    }
+
     void setConstant( const BaseTypeVariant& var )
     {
         m_constant = true;
@@ -298,24 +302,11 @@ private:
 
 ///////////////////////////////////////////////////////////////////////////////////
 
-class UdtTypeInfo : public TypeInfo 
+class UdtFieldColl : public TypeInfo
 {
-public:
-
-    UdtTypeInfo (SymbolPtr &symbol ) :
-        m_dia( symbol ),
-        m_fields( symbol->getName() )
-    {
-    }
-
 protected:
-
     virtual std::string getName() {
-        return m_dia->getName();
-    }
-
-    virtual ULONG getSize() {
-        return (ULONG)m_dia->getSize();
+        return m_fields.getName();
     }
 
     virtual TypeInfoPtr getField( const std::string &fieldName ) {
@@ -331,7 +322,7 @@ protected:
     }
 
     virtual ULONG getFieldOffsetByNameRecirsive( const std::string &fieldName ) {
-        return UdtUtils::getFiledOffsetRecirsive( shared_from_this(), fieldName );
+        return UdtUtils::getFieldOffsetRecirsive( shared_from_this(), fieldName );
     }
 
     virtual ULONG getFieldOffsetByNameNotRecursively( const std::string &fieldName ) {
@@ -342,10 +333,9 @@ protected:
         return lookupField(index).m_offset;
     }
 
-    virtual ULONG getFieldCount();
-
-    virtual bool isUserDefined() {
-        return true;
+    virtual ULONG getFieldCount() {
+        refreshFields();
+        return (ULONG)m_fields.size();
     }
 
     virtual ULONG getElementCount() {
@@ -358,9 +348,61 @@ protected:
 
     virtual std::string print();
 
-    SymbolPtr    m_dia;
+    virtual bool isUserDefined() {
+        return true;
+    }
 
-    UdtUtils::FieldCollection  m_fields;
+protected:
+    UdtFieldColl(const std::string &typeName) : m_fields(typeName) {}
+
+    virtual void refreshFields() {}
+    virtual std::string getTypeString() const = 0;
+
+    bool empty() const {
+        return m_fields.empty();
+    }
+
+    void push_back(const UdtUtils::Field &field) {
+        m_fields.push_back(field);
+    }
+
+    template <typename T>
+    const UdtUtils::Field &lookupField( T index) {
+        refreshFields();
+        return m_fields.lookup(index);
+    }
+
+    UdtUtils::Field &last(){
+        return *m_fields.rbegin();
+    }
+
+private:
+    UdtUtils::FieldCollection m_fields;
+};
+
+///////////////////////////////////////////////////////////////////////////////////
+
+class UdtTypeInfo : public UdtFieldColl
+{
+public:
+
+    UdtTypeInfo (SymbolPtr &symbol ) :
+        UdtFieldColl( symbol->getName() ),
+        m_dia( symbol )
+    {
+    }
+
+protected:
+    virtual ULONG getSize() {
+        return (ULONG)m_dia->getSize();
+    }
+    void getVirtualFields();
+
+    virtual void refreshFields() override;
+
+    virtual std::string getTypeString() const override {
+        return "struct/class";
+    }
 
     void getFields( 
         SymbolPtr &rootSym, 
@@ -371,16 +413,8 @@ protected:
         ULONG m_virtualDispSize = 0 );
 
 
-    void getVirtualFields();
-
 private:
-    void refreshFields();
-
-    template <typename T>
-    const UdtUtils::Field &lookupField( T index) {
-        refreshFields();
-        return m_fields.lookup(index);
-    }
+    SymbolPtr m_dia;
 };
 
 ///////////////////////////////////////////////////////////////////////////////////
diff --git a/pykd/udtutils.cpp b/pykd/udtutils.cpp
index 7ff0efe..5b8fc01 100644
--- a/pykd/udtutils.cpp
+++ b/pykd/udtutils.cpp
@@ -36,7 +36,7 @@ const Field &FieldCollection::lookup(const std::string &name) const
 
 ///////////////////////////////////////////////////////////////////////////////////
 
-ULONG getFiledOffsetRecirsive(TypeInfoPtr typeInfo, const std::string &fieldName)
+ULONG getFieldOffsetRecirsive(TypeInfoPtr typeInfo, const std::string &fieldName)
 {
     // "m_field1.m_field2" -> ["m_field1", "m_field2"]
     typedef boost::char_separator<char> CharSep;
diff --git a/pykd/udtutils.h b/pykd/udtutils.h
index b32a818..29aec43 100644
--- a/pykd/udtutils.h
+++ b/pykd/udtutils.h
@@ -46,13 +46,17 @@ public:
     const Field &lookup(ULONG index) const;
     const Field &lookup(const std::string &name) const;
 
+    const std::string &getName() const {
+        return m_baseTypeName;
+    }
+
 private:
     std::string m_baseTypeName;
 };
 
 ///////////////////////////////////////////////////////////////////////////////////
 
-ULONG getFiledOffsetRecirsive(TypeInfoPtr typeInfo, const std::string &fieldName);
+ULONG getFieldOffsetRecirsive(TypeInfoPtr typeInfo, const std::string &fieldName);
 
 ///////////////////////////////////////////////////////////////////////////////////
 
diff --git a/test/scripts/customtypestest.py b/test/scripts/customtypestest.py
new file mode 100644
index 0000000..750d824
--- /dev/null
+++ b/test/scripts/customtypestest.py
@@ -0,0 +1,72 @@
+"""Custom types tests"""
+
+import unittest
+import target
+import pykd
+
+class CustomTypesTest(unittest.TestCase):
+    def testCommonStruct(self):
+        mySubStruct = pykd.createStruct("MySubCustomStruct")
+        mySubStruct.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        mySubStruct.append( "m_uint2", pykd.typeInfo("UInt2B") )
+
+        mySubUnion = pykd.createUnion("MySubCustomUnion")
+        mySubUnion.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        mySubUnion.append( "m_uint2", pykd.typeInfo("UInt2B") )
+
+        myType = pykd.createStruct("MyCustomStruct")
+        myType.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        myType.append( "m_uint4", pykd.typeInfo("UInt4B") )
+        myType.append( "m_uint2", pykd.typeInfo("UInt2B") )
+        myType.append( "m_struct", mySubStruct )
+        myType.append( "m_union", mySubUnion )
+        myType.append( "m_uint8", pykd.typeInfo("UInt8B") )
+
+        self.assertTrue( myType.size() != 0 )
+        self.assertTrue( myType.size() >= myType.fieldOffset("m_uint8") + myType.m_uint8.size() )
+        
+        self.assertTrue( myType.fieldOffset("m_uint1") == 0 )
+
+        self.assertTrue( myType.fieldOffset("m_uint1") < myType.fieldOffset("m_uint4") )
+        self.assertTrue( myType.fieldOffset("m_uint1") + myType.m_uint1.size() <= myType.fieldOffset("m_uint4") )
+
+        self.assertTrue( myType.fieldOffset("m_uint4") < myType.fieldOffset("m_uint2") )
+        self.assertTrue( myType.fieldOffset("m_uint4") + myType.m_uint4.size() <= myType.fieldOffset("m_uint2") )
+
+        self.assertTrue( myType.fieldOffset("m_uint2") < myType.fieldOffset("m_struct") )
+        self.assertTrue( myType.fieldOffset("m_uint2") + myType.m_uint2.size() <= myType.fieldOffset("m_struct") )
+
+        self.assertTrue( myType.fieldOffset("m_struct") < myType.fieldOffset("m_union") )
+        self.assertTrue( myType.fieldOffset("m_struct") + myType.m_struct.size() <= myType.fieldOffset("m_union") )
+
+        # print myType
+
+    def testCommonUnion(self):
+        myType = pykd.createUnion("MyCustomStruct")
+        myType.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        myType.append( "m_uint4", pykd.typeInfo("UInt4B") )
+        myType.append( "m_uint2", pykd.typeInfo("UInt2B") )
+
+        self.assertFalse( myType.size() == 0 )
+        self.assertTrue( myType.fieldOffset("m_uint1") == 0 )
+        self.assertTrue( myType.fieldOffset("m_uint4") == 0 )
+        self.assertTrue( myType.fieldOffset("m_uint2") == 0 )
+
+    def testDupFieldName(self):
+        myType = pykd.createStruct("MyCustomStruct")
+        exceptionRised = False
+        myType.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        try:
+            myType.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        except pykd.TypeException:
+            exceptionRised = True
+        self.assertTrue(exceptionRised)
+
+        myType = pykd.createUnion("MyCustomStruct")
+        exceptionRised = False
+        myType.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        try:
+            myType.append( "m_uint1", pykd.typeInfo("UInt1B") )
+        except pykd.TypeException:
+            exceptionRised = True
+        self.assertTrue(exceptionRised)
diff --git a/test/scripts/pykdtest.py b/test/scripts/pykdtest.py
index f32efe2..d2cd68c 100644
--- a/test/scripts/pykdtest.py
+++ b/test/scripts/pykdtest.py
@@ -20,6 +20,7 @@ import typeinfo
 import typedvar
 import regtest
 import localstest
+import customtypestest
 
 class StartProcessWithoutParamsTest(unittest.TestCase):
     def testStart(self):
@@ -45,6 +46,7 @@ def getTestSuite( singleName = "" ):
                 unittest.TestLoader().loadTestsFromTestCase( typeinfo.TypeInfoTest ),
                 unittest.TestLoader().loadTestsFromTestCase( typedvar.TypedVarTest ),
                 unittest.TestLoader().loadTestsFromTestCase( regtest.CpuRegTest ),
+                unittest.TestLoader().loadTestsFromTestCase( customtypestest.CustomTypesTest ),
                 # ^^^
                 unittest.TestLoader().loadTestsFromTestCase( TerminateProcessTest ),
 
diff --git a/test/targetapp/targetapp.vcproj b/test/targetapp/targetapp.vcproj
index ec9f910..226ad86 100644
--- a/test/targetapp/targetapp.vcproj
+++ b/test/targetapp/targetapp.vcproj
@@ -408,6 +408,10 @@
 				RelativePath="..\scripts\clienttest.py"
 				>
 			</File>
+			<File
+				RelativePath="..\scripts\customtypestest.py"
+				>
+			</File>
 			<File
 				RelativePath="..\scripts\dbgcmd.py"
 				>