Atypical teratoid/rhabdoid tumor rarely occurs in the CNS, though is most common in infants under two years of age. It is characterized by unique histologic features, has an extremely aggressive natural course, and is located mainly in the infratentorial region. Radiologically, it is difficult to distinguish from primitive neuroectodermal tumor or medulloblastoma. We report the radiologic findings of two cases of atypical teratoid/rhabdoid tumor.