Tracheobronchomegaly, seen in Mounier-Kuhn syndrome, is an abnormal diffuse dilatation of the trachea and main bronchi. The diagnosis of tracheobronchomegaly is usually apparent on chest radiographs, CT, and MR. Typically, there is protrusion of the mucosa through the trachealis muscle between the cartilaginous rings, producing a scalloped or corrugated appearance of the trachea and main bronchi.