Cerebral primitive neuroectodermal tumor(PNET), consisting of undifferentiated primitive cells, is a neoplasm of children and young adults that occurs predominantly in the supratentorial compartment. In this report, we retrospectively reviewed and analyzed 18 CT and 6 MR findings in 18 patients with pathologically-proven PNET to discover the characteristic findings, if any. The most characteristic feature of the PNETs was a well-defined multilobular oval or round large mass with components of peripheral cystic change or calcification in the cerebral hemisphere, especially in the parietal lobe. Usually there was only minimal surrounding edema. The CT density of the tumor was iso-or slightly high density with homogeneous contrast enhancement in the solid portion and low density in the cystic area. MR findings demonstrated is0-singal intensity on both T1-weighted(T1W1) and T2-weighted(T2WI) images and dense enhancement in the solid element. The cystic portion revealed low intensity on T1W1 and high intensity on T2WI.