diff --git a/ide/ideprocs.pp b/ide/ideprocs.pp
index 2918fc56af..22ebb6f897 100644
--- a/ide/ideprocs.pp
+++ b/ide/ideprocs.pp
@@ -30,7 +30,7 @@ unit IDEProcs;
 interface
 
 uses
-  Classes, SysUtils, Laz_XMLCfg, FileUtil, LCLProc,
+  Classes, SysUtils, Laz_XMLCfg, FileUtil, LCLProc, AvgLvlTree,
   FileProcs, LazConf;
 
 type
@@ -162,6 +162,10 @@ procedure LoadStringList(XMLConfig: TXMLConfig; List: TStrings;
                          const Path: string);
 procedure SaveStringList(XMLConfig: TXMLConfig; List: TStrings;
                          const Path: string);
+procedure LoadStringToStringTree(XMLConfig: TXMLConfig;
+                                 Tree: TStringToStringTree; const Path: string);
+procedure SaveStringToStringTree(XMLConfig: TXMLConfig;
+                                 Tree: TStringToStringTree; const Path: string);
 procedure MakeXMLName(var Name: string);
   
 
@@ -854,6 +858,46 @@ begin
     XMLConfig.SetDeleteValue(Path+'Item'+IntToStr(i+1)+'/Value',List[i],'');
 end;
 
+procedure LoadStringToStringTree(XMLConfig: TXMLConfig;
+  Tree: TStringToStringTree; const Path: string);
+var
+  Cnt: LongInt;
+  SubPath: String;
+  CurName: String;
+  CurValue: String;
+  i: Integer;
+begin
+  Tree.Clear;
+  Cnt:=XMLConfig.GetValue(Path+'Count',0);
+  for i:=0 to Cnt-1 do begin
+    SubPath:=Path+'Item'+IntToStr(i)+'/';
+    CurName:=XMLConfig.GetValue(SubPath+'Name','');
+    CurValue:=XMLConfig.GetValue(SubPath+'Value','');
+    Tree.Values[CurName]:=CurValue;
+  end;
+end;
+
+procedure SaveStringToStringTree(XMLConfig: TXMLConfig;
+  Tree: TStringToStringTree; const Path: string);
+var
+  Node: TAvgLvlTreeNode;
+  Item: PStringToStringItem;
+  i: Integer;
+  SubPath: String;
+begin
+  XMLConfig.SetDeleteValue(Path+'Count',Tree.Tree.Count,0);
+  Node:=Tree.Tree.FindLowest;
+  i:=0;
+  while Node<>nil do begin
+    Item:=PStringToStringItem(Node.Data);
+    SubPath:=Path+'Item'+IntToStr(i)+'/';
+    XMLConfig.SetDeleteValue(SubPath+'Name',Item^.Name,'');
+    XMLConfig.SetDeleteValue(SubPath+'Value',Item^.Value,'');
+    Node:=Tree.Tree.FindSuccessor(Node);
+    inc(i);
+  end;
+end;
+
 procedure MakeXMLName(var Name: string);
 var
   i: Integer;
diff --git a/ide/project.pp b/ide/project.pp
index e1ce39c3ab..218aa3a2bc 100644
--- a/ide/project.pp
+++ b/ide/project.pp
@@ -1686,6 +1686,9 @@ function TProject.WriteProject(ProjectWriteFlags: TProjectWriteFlags;
       FJumpHistory.DeleteInvalidPositions;
       FJumpHistory.SaveToXMLConfig(aConfig,Path);
     end;
+    
+    // save custom session data
+    SaveStringToStringTree(aConfig,CustomSessionData,Path+'CustomSessionData/');
   end;
 
 var
@@ -1789,6 +1792,9 @@ begin
       xmlconfig.SetDeleteValue(Path+'VersionInfo/OriginalFilename/Value', VersionInfo.OriginalFilenameString,'');
       xmlconfig.SetDeleteValue(Path+'VersionInfo/ProductName/Value', VersionInfo.ProdNameString,'');
 
+      // save custom data
+      SaveStringToStringTree(xmlconfig,CustomData,Path+'CustomData/');
+
       // Save the compiler options
       CompilerOptions.SaveToXMLConfig(XMLConfig,'CompilerOptions/');
       
@@ -2058,6 +2064,9 @@ var
     ActiveEditorIndexAtStart := xmlconfig.GetValue(
        Path+'General/ActiveEditorIndexAtStart/Value', -1);
     FJumpHistory.LoadFromXMLConfig(xmlconfig,Path+'');
+
+    // load custom session data
+    LoadStringToStringTree(xmlconfig,CustomSessionData,Path+'CustomSessionData/');
   end;
   
   procedure LoadDefaultSession;
@@ -2166,6 +2175,9 @@ begin
       VersionInfo.OriginalFilenameString := xmlconfig.GetValue(Path+'VersionInfo/OriginalFilename/Value', '');
       VersionInfo.ProdNameString := LineBreaksToSystemLineBreaks(xmlconfig.GetValue(Path+'VersionInfo/ProductName/Value', ''));
 
+      // load custom data
+      LoadStringToStringTree(xmlconfig,CustomData,Path+'CustomData/');
+      
       {$IFDEF IDE_MEM_CHECK}CheckHeapWrtMemCnt('TProject.ReadProject update ct boss');{$ENDIF}
       CodeToolBoss.GlobalValues.Variables[ExternalMacroStart+'ProjPath']:=
                                                                ProjectDirectory;
diff --git a/ideintf/projectintf.pas b/ideintf/projectintf.pas
index 7cff683469..0fdf402567 100644
--- a/ideintf/projectintf.pas
+++ b/ideintf/projectintf.pas
@@ -22,8 +22,8 @@ unit ProjectIntf;
 interface
 
 uses
-  Classes, SysUtils, LCLProc, FileUtil, Controls, Forms, NewItemIntf,
-  ObjInspStrConsts;
+  Classes, SysUtils, LCLProc, FileUtil, Controls, Forms, AvgLvlTree,
+  NewItemIntf, ObjInspStrConsts;
 
 const
   FileDescGroupName = 'File';
@@ -518,6 +518,8 @@ type
 
   TLazProject = class(TPersistent)
   private
+    FCustomData: TStringToStringTree;
+    FCustomSessionData: TStringToStringTree;
     FLazCompilerOptions: TLazCompilerOptions;
     fModified: boolean;
     FProjectSessionFile: string;
@@ -582,6 +584,8 @@ type
                        // units have their own SessionModified
     property LazDocPaths: string read FLazDocPaths write SetLazDocPaths;
     property RSTOutputDirectory: string read FRSTOutputDirectory write SetRSTOutputDirectory;
+    property CustomData: TStringToStringTree read FCustomData;
+    property CustomSessionData: TStringToStringTree read FCustomSessionData;
   end;
 
   TLazProjectClass = class of TLazProject;
@@ -1117,10 +1121,14 @@ constructor TLazProject.Create(ProjectDescription: TProjectDescriptor);
 begin
   inherited Create;
   FSessionStorage:=pssInProjectInfo;
+  FCustomData:=TStringToStringTree.Create(true);
+  FCustomSessionData:=TStringToStringTree.Create(true);
 end;
 
 destructor TLazProject.Destroy;
 begin
+  FreeAndNil(FCustomData);
+  FreeAndNil(FCustomSessionData);
   inherited Destroy;
 end;