procedure TForm1.TreeView1Click(Sender: TObject); 
var 
  s: string; 
  p: TPoint; 
begin 
  GetCursorPos(p); 
  p := TreeView1.ScreenToClient(p); 
  if htOnLabel in TreeView1.GetHitTestInfoAt(p.x, p.y) 
    then begin 
    s := TreeView1.GetNodeAt(p.x, p.y).Text; 
    showmessage(s); // z.B.: 
  end; 
end;