The ganglioneuroma is a benign neuroblastal tumor. All neuroblastomas and ganglioneuromas derive from immature cells of the sympathetic nerve system. The ganglioneuroma is a very rare disease and effects newborns and infants more often than adolescents and adults. The benign tumors are relatively difficult to diagnose since they usually are asymptomatic. A 5-year old girl with persistent bladder wall thickening and prominent course of the prevesical ureter presents for diagnosis and therapy. Sonography demonstrated a space-occupying lesion of the left kidney. Subsequent MRI raises the suspicion of a retroperitoneal neuroblastoma. The tumor could be removed in two surgical sessions. The ganglioneuroma is a benign tumor with symptoms depending on location and with a relatively good prognosis. Its low incidence and resultant limited experience often leads to delayed diagnosis, potentially determining therapy and diagnosis.