We report a case of mediastinal lymphangioma associated with Gorham's disease in a 38-year-old man who had suffered recurrent clavicular fractures during a seven-year period. Mediastinal widening associated with osteolysis of the clavicles and the sternal manubrium was revealed by chest radiography, while computed tomography demonstrated a cystic anterior mediastinal mass infiltrating mediastinal fat and associated with osseous destruction of the clavicles and manubrium. Chylothorax recurred during the course of the disease.