Mediastinal ganglioneuroma is infrequently encountered in childhood. The posterior mediastinal ganglioneuroma which extended the contralateral thorax was very rare. A 4-year-old boy had a ganglioneuroma which involved bilateral thorax and encased the aorta and azygous vein and the ganglioneuroma was successfully extirpated by two-staged operations.; left thoracotomy first right thoracotomy 10days later.