Germ cell tumor exists as a primary entity in the anterior mediastinum. In a CT study of two males and one female with primary non-seminomatous germ cell tumors all masses were large and lobulated with a mixed density. The fat planes were for the most part obliterated. A high attenuating border was present around parts of the tumor in all three cases, and the pleura-lung interfaces were irregular. One patient had pericardial and left pleural effusions as well as tumor invasion of the anterior chest wall. An extragonadal germ cell tumor should be considered when CT of the thorax reveals a large mass in the anterior mediastinum of a young adult.