procedure TForm1.FormCreate(Sender: TObject);
var I, MaxWidth: integer;
begin
MaxWidth:=0;
for i:=0 to listbox1.Items.Count -1 do
if MaxWidth<Listbox1.Canvas.TextWidth(Listbox1.Items.Strings[i]) then
MaxWidth:=Listbox1.Canvas.TextWidth(Listbox1.Items.Strings[i]);
SendMessage(listbox1.handle,LB_SetHorizontalextent,maxWidth+2,0)
end;