We report on the very rare case of a 49-year-old man with a large solitary pulmonary lymphangioma. Rapid growth of the tumor led to dyspnea and pain. A chest roentgenogram and computed tomography scan revealed a large 18 x 12-cm space-occupying cystic lesion in the posterior mediastinum. The tumor was resected by lateral thoracotomy. Histopathology revealed a pulmonary cystic lymphangioma.