Mounier-Kuhn syndrome or congenital tracheobronchomegaly is a rare clinical and radiologic condition. It is characterized by a tracheal and bronchial dilation. Fewer than 100 cases have been reported in the medical literature since the original description in 1932. The first utilization of bronchoscopy for diagnosis of this condition was recorded by Lemoine only in 1949. The cause of this condition is not clearly understood; however, histopathologic findings of atrophy of smooth muscles and elastic tissue in the trachea and main bronchi have been observed. Tracheobronchomegaly can be associated with tracheal and bronchial diverticuli.