Computed tomographic findings in fifteen cases of anterior mediastinal teratoma are presented and compared with radiographic, and pathologic findings. Specific CT characteristics of anterior mediastinal teratoma are predominantly fatty mass with a denser depedent and globular calcification in a solid protuberance into the cystic cavity. Six cases presented above described characteristic CT findings. Four cases presented water density mass with surrounding thick wall. Fat and calcific densities were present in nine and seven respectively, so these findings are frequently absent. Thick wall was present in all cases. So thick walled cyst even in the absence of fatty or calcific densities is highly suggestive of anterior mediastinal teratoma.