try this .. Add a tooltip to manage your Forms and write this code in the DrawItem event to manage the list with the list
drawmode combobox, OwnerDrawFixed
if (e.Index == -1) { return; }
Point p = new Point(ComboBox1.Location.X + 120, ComboBox1.Location.Y + ComboBox1.Height + (30 + e.Index * 10));
if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
{
toolTip.Show(ComboBox1.Items[e.Index].ToString(), this, p);
}
e.DrawBackground();
e.Graphics.DrawString(ComboBox1.Items[e.Index].ToString(), e.Font, Brushes.Black, new Point(e.Bounds.X, e.Bounds.Y));