Tracheobronchomegaly or Mounier-Kuhn syndrome a is rare disease characterized by marked dilatation of the trachea and main bronchi. It is thought to be due to a congenital anomaly, but is uncertain. It has variable clinical manifestations from causing chronic respiratory infections and bronchiectasis to being asymptomatic for the lifetime. Recently, we experienced a case of Mounier-Kuhn syndrome patient with tracheal diverticulum, who had lung cancer. Our case is reported with literature reviews.