diff --git a/ide/environmentopts.pp b/ide/environmentopts.pp
index 6965b9dc3e..7b2ec26610 100644
--- a/ide/environmentopts.pp
+++ b/ide/environmentopts.pp
@@ -162,6 +162,9 @@ type
     FHideIDEOnRun: boolean;
     FHideMessagesIcons: boolean;
     FComponentPaletteVisible: boolean;
+    // CompletionWindow
+    FCompletionWindowWidth: Integer;
+    FCompletionWindowHeight: Integer;
 
     // designer
     FCreateComponentFocusNameProperty: boolean;
@@ -342,6 +345,11 @@ type
     property IDESpeedButtonsVisible: boolean read FIDESpeedButtonsVisible
                                              write FIDESpeedButtonsVisible;
 
+    property CompletionWindowWidth: Integer read FCompletionWindowWidth
+                                            write FCompletionWindowWidth;
+    property CompletionWindowHeight: Integer read FCompletionWindowHeight
+                                             write FCompletionWindowHeight;
+
     // EnvironmentOptionsDialog editor
     property ShowBorderSpacing: boolean read FShowBorderSpacing write FShowBorderSpacing;
     property ShowGrid: boolean read FShowGrid write FShowGrid;
@@ -930,6 +938,10 @@ begin
         Path+'Desktop/ComponentPaletteVisible/Value',true);
       FIDESpeedButtonsVisible:=XMLConfig.GetValue(
         Path+'Desktop/IDESpeedButtonsVisible/Value',true);
+      FCompletionWindowWidth:=XMLConfig.GetValue(
+        Path+'Desktop/CompletionWindowWidth/Value', 320);
+      FCompletionWindowHeight:=XMLConfig.GetValue(
+        Path+'Desktop/CompletionWindowHeight/Value', 6);
 
       // EnvironmentOptionsDialog editor
       FShowGrid:=XMLConfig.GetValue(
@@ -1250,6 +1262,10 @@ begin
                                FComponentPaletteVisible,true);
       XMLConfig.SetDeleteValue(Path+'Desktop/IDESpeedButtonsVisible/Value',
                                FIDESpeedButtonsVisible,true);
+      XMLConfig.SetDeleteValue(Path+'Desktop/CompletionWindowWidth/Value',
+                               FCompletionWindowWidth, 320);
+      XMLConfig.SetDeleteValue(Path+'Desktop/CompletionWindowHeight/Value',
+                               FCompletionWindowHeight, 6);
 
       // EnvironmentOptionsDialog editor
       XMLConfig.SetDeleteValue(Path+'FormEditor/ShowBorderSpacing',
diff --git a/ide/sourceeditor.pp b/ide/sourceeditor.pp
index e8df5d358e..eefe7b7408 100644
--- a/ide/sourceeditor.pp
+++ b/ide/sourceeditor.pp
@@ -57,7 +57,7 @@ uses
   SrcEditorIntf, MenuIntf, LazIDEIntf, PackageIntf, IDEHelpIntf, IDEImagesIntf,
   IDEWindowIntf, ProjectIntf,
   // IDE units
-  IDEDialogs, LazarusIDEStrConsts, IDECommands, EditorOptions,
+  IDEDialogs, LazarusIDEStrConsts, IDECommands, EditorOptions, EnvironmentOpts,
   WordCompletion, FindReplaceDialog, IDEProcs, IDEOptionDefs,
   MacroPromptDlg, TransferMacros, CodeContextForm, SrcEditHintFrm, MsgView, InputHistory, CodeMacroPrompt,
   CodeTemplatesDlg, CodeToolsOptions,
@@ -108,6 +108,7 @@ type
   { TSourceEditCompletion }
 
   TSourceEditCompletion=class(TSynCompletion)
+    procedure CompletionFormResized(Sender: TObject);
   private
     FIdentCompletionJumpToError: boolean;
     ccSelection: String;
@@ -1423,6 +1424,12 @@ end;
 
 { TSourceEditCompletion }
 
+procedure TSourceEditCompletion.CompletionFormResized(Sender: TObject);
+begin
+  EnvironmentOptions.CompletionWindowWidth  := TheForm.Width;
+  EnvironmentOptions.CompletionWindowHeight := TheForm.NbLinesInWindow;
+end;
+
 procedure TSourceEditCompletion.ccExecute(Sender: TObject);
 // init completion form
 // called by OnExecute just before showing
@@ -1970,6 +1977,10 @@ begin
   OnUTF8KeyPress:=@OnSynCompletionUTF8KeyPress;
   OnPositionChanged:=@OnSynCompletionPositionChanged;
   ShortCut:=Menus.ShortCut(VK_UNKNOWN,[]);
+  TheForm.ShowSizeDrag := True;
+  TheForm.Width := EnvironmentOptions.CompletionWindowWidth;
+  TheForm.NbLinesInWindow := EnvironmentOptions.CompletionWindowHeight;
+  TheForm.OnDragResized  := @CompletionFormResized;
 end;
 
 { TSourceEditorSharedValues }