function GetColumnIndex(pListView: TListView; CursorX: Integer): Integer;
var
  WidthOffset: Integer;
begin
  WidthOffset := 0;
  Result := NEGATIVE_INDEX;
  if pListView = nil then
    Exit;
  while CursorX > WidthOffset do
  begin
    Inc(Result, 1);
    Inc(WidthOffset, pListView.Columns[Result].Width);
  end;
end;

procedure TFrom1.ListView1SelectItem(Sender: TObject; Item: TListItem;
  Selected: Boolean);
var
  p: TPoint;
  nBegColPos, I: Integer;
begin
  GetCursorPos(p);
  p := ListView1.ScreenToClient(p);
  I := GetColumnIndex(ListView1, p.X);
  if I = 9 then
  begin
    nBegColPos := (ListView1.Width - ListView1.Columns[9].Width);
    if (p.X = nBegColPos) or (p.X <= (nBegColPos + ImageList1.Width)) then
      ShowMessage('Иконка SubItem #9')
    else
      ShowMessage('Это не иконка');
  end;
end;