Teratomas, usually arising in the anterior mediastinum, are very uncommon in the posterior mediastinum, Embryologic development of anterior mediastinal teratoma is thought to be from thymic anlage which descends from the third branchial cleft and pouch, while that of posterior mediastinal teratoma is thought to be from the remnant of notochord. CT findings of posterior mediastinal teratomas are not different from teratomas elsewhere, containing fat, calcification, soft tissue and thick walled cyst. Ultrasonographic findings are mixed echogenic mass containing cystic portion, highly reflective solid portion and area of acoustic shadowing. Authors recently experienced 2 cases of surgically proven posterior mediastinal teratoma and reoprt with review of literature.