Tracheobronchomegaly is a rare disorder of the lower respiratory tract characterised by marked dilatation of the trachea and the central bronchi associated with recurrent respiratory tract infections. However, some patients with tracheobronchomegaly are not detected because the symptoms are overlooked if chest radiographs alone are used for diagnosis. We encountered two cases of tracheobronchomegaly that were not diagnosed by chest radiographic examinations but were shown clearly with CT. We believe that patients with recurrent pulmonary infection must be examined with the use of CT.