Forty-three children with CT studies demonstrating abnormalities in the posterior fossa are presented. Tumors constitute the largest group of lesions (53.5%). Their mean size at time of diagnosis was 39.5 mm. Astrocytomas, medulloblastomas, and ependymomas were the most frequent tumors and their CT features are described and discussed. The congenital group of lesions comprised 18.6% of the cases--the most frequent anomaly being arachnoid cyst. In the miscellaneous group (23.3%), cases with atrophy were the most frequent. The cerebellar hemispheres were the most involved sites (39.5%). Lesions located at the tentorial hiatus or near the clivus were rather rare.