A unique case of ganglioneuroma mimicking a lipomatous tumor in a 73-year-old man is reported. The tumor was incidentally found on radiography performed for unrelated reasons. Because of the fat element, CT and magnetic resonance imaging suggested myelolipoma inside or outside the right adrenal gland. The laparotomy indicated that the tumor was located on the right adrenal gland. It was well circumscribed but not encapsulated, and was approximately 2 cm in diameter. Microscopically, ganglioneuromatous component was scattered in the background of a large amount of adipose tissue. Because the presence of such a large amount of adipose tissue seems to be rare in ganglioneuromas, its histogenesis is discussed.