There is no such property in TListBox. To force a listbox to have horizontal scrollbars, use the message LB_SETHORIZONTALEXTENT.
// e.g. in FormCreate(..)
begin
ListBox1.Width := 300;
// listbox can be scrolled by 100 pixels horizontally now:
SendMessage (ListBox1.Handle, LB_SETHORIZONTALEXTENT, 400, 0);
end;