Ganglioneuroma is relatively rare, and difficult to distinguish from other tumors due to lack of image findings specific for ganglioneuromas. In this report, two cases of ganglioneuroma preoperatively diagnosed as non-functioning adrenal tumor and retroperitoneal tumor are reported. A 25-year-old male and a 29-year-old male visited our institute with chief complaints of upper abdominal pain and asymptomatic microscopic hematuria, respectively. Computed tomographic scan and magnetic resonance imaging showed a 7 x 6 x 5 cm solid tumor above the upper pole of the right kidney in the former case, 8 cm poorly enhanced tumor grown surrounding the left renal artery in the latter case. Surgical resection was performed in both cases. In the latder case, since intraoperative histological examination showed no malignant finding, renal vessels penetrating in the tumor were preserved by transecting the tumor. Postoperative histological examination revealed an adrenal ganglioneuroma and a retroperitoneal ganglioneuroma in the former and latter cases, respectively. A ganglioneuroma can be surgically dissected with favorable prognosis, but preoperative differential diagnosis is sometimes difficult due to few specific radiological and laboratory findings.