uses CommCtrl; 
 
var 
  ln: TTreeNode; 
 
function NodeBold(node: TTreeNode; bld: Boolean): TTreeNode; 
var 
  tvi: TTVItem; 
begin 
  if node <> nil then begin 
    zeromemory(@tvi, SizeOf(tvi)); 
    tvi.hItem := node.ItemID; 
    tvi.Mask := TVIF_STATE; 
    tvi.StateMask := TVIS_BOLD; 
    if bld then tvi.State := TVIS_BOLD 
    else tvi.State := 0; 
    TreeView_SetItem(node.Handle, tvi); 
    result := node; 
  end else result := nil; 
end; 
 
procedure TForm1.TreeView1Change(Sender: TObject; Node: TTreeNode); 
begin 
  NodeBold(ln, FALSE); 
  ln := NodeBold(TreeView1.Selected, TRUE); 
end; 
 
procedure TForm1.FormShow(Sender: TObject); 
begin 
 Treeview1.setfocus; 
end;