A nodular neuroblastoma was partially removed from the cerebellar vermis of a 15-month-old boy. Postoperative irradiation and chemotherapy were performed. More than 5 years later, re-operation revealed a mature ganglioglioma. Problems relating to the maturation of ganglionic tumors are discussed. The present case emphasizes that it is not justified to regard all neuroblastomas of the central nervous system as highly malignant neoplasms (grade IV).