A 14-year-old boy presented with cerebellar ganglioglioma manifesting as severe headache and confusion. Computed tomographic scans showed a huge, partly enhanced cystic cerebellar tumor. The tumor was totally removed. Histological examination disclosed glial cells and mature ganglion cells. The latter were identified by Nissl's staining and immunostaining for neurofilaments. Ganglion cells were present in the cerebellum and the surrounding subarachnoid space. This heterotopic growth of ganglion cells enabled a firm diagnosis of cerebellar ganglioglioma.