A majority of incidentally found adrenal tumors derive from the adrenal cortex. The aim of our study was evaluation of the incidence of chromaffin tumors in a group of 1,111 patients with adrenal incidentalomas. In this group there were 803 women and 308 men, aged 10-87 years. Clinical examination, imaging studies (ultrasound scans, CT, and MRI if necessary), and hormonal determinations (cortisol, ACTH and androgens in the blood, dexamethasone suppression test, urinary excretion of 17-OHCS, aldosterone and 17-KS, as well as PRA/aldosterone stimulation test and metanephrines in hypertensive patients and those with density in CT over 20 HU) were used. In 380 patients treated by surgery (mainly by laparoscopic approach), histological and immunocytochemical examinations were performed. Clinical examination revealed hypertension in 25% of the patients under study. Chromaffin tumors were detected in 43 patients, 33 women, and 10 men aged 20-75 years: pheochromocytoma in 36 (malignant in 3); chromaffin cells hyperplasia in 2; paraganglioma in 3; ganglioneuroblastoma in 1; ganglioneuroma in 1; and schwannoma in 2. The tumors' diameter ranged between 1.1 and 20.0 cm, density=25 Hounsfield units (HU) or more before contrast medium injection. Hypertension was present in 53% of these patients. The urinary metanephrines excretion was elevated in 31 of 38 patients, in whom the determinations were done. Chromaffin tumors were detected in 4% (pheochromocytomas in 3%) of 1,111 patients with adrenal incidentalomas. Malignancy was present in 9% of 43 patients with chromaffin tumors. High density in CT was a very important diagnostic finding in the incidentally found medullary tumors.