The aim of the study was to determine the prevalence of adrenal tumours and their types based on the analysis of material from university surgical centres participating in a 5-year study between the years 2001 and 2005.Material and methods. A total of 178 patients, 169 (94.9%) adults and 9 (5.1%) children, with adrenal tumours were treated during the study period. Amongst the operated upon patients, there were 111 (62.4%) females (106 adults and 5 girls) and 67 (37.6%) males (63 adults and 4 boys). The age of patients ranged from 7 months to 82 years (mean 55.4 ± 11.8 years). For children, ages ranged from 7 months to 17 years, while for adults ages ranged from 24 to 82 years.Results. Incidentalomas were detected in 36 (21.3%) of 169 adults, and seven (19.4%) of them were found to be hormonally active in biochemical tests.The patients underwent surgery after the preparation depending on the general state, type of tumour, its functioning, and concomitant diseases. Adrenalectomy was performed using a classical open technique through the lumbal access in 146 (86.4%) adults, and a laparoscopic technique through the retro- or transperitoneal access in 23 (13.6%) adults. In the videolaparoscopic operations, retroperitoneal access was preferred. All children were operated upon by means of the classical technique with trans-abdominal access.Adrenal tumours were most frequent in the 6th decade of life (33.2% of all tumours). In the adult group, 143 (84.6%) cases of histologically diagnosed benign tumours and 26 (15.4%) cases of malignant neoplasms were found. Sixteen (9.5% of all tumours and 61.5% of malignancies) of them appeared to be secondary metastatic tumours. Moreover, six (66.7%) children had primary malignant adrenal tumours.In three adult patients whose tumours were up to 3 cm in size in the remaining adrenal gland (after previous adrenalectomy on the other side), enucleation was carried out in one patient and partial resection of the only adrenal gland in two patients. The follow-up cortisol levels in the blood sera of these patients appeared to be normal.Conclusions. 1. Adrenal tumours most commonly occur in the 6th and 7th decades of patients' lives; an increase in the incidence rate is affected by the percentage of metastases to adrenal glands. 2. Adrenal incidentalomas reveal subclinical hormonal activity in a significant percentage of patients and require adequate preparation prior to surgery. 3. Operations preserving the cortex of the only adrenal gland allow the patients to avoid hormonal substitution therapy. 4. Tumours in children are a separate phenomenon with specific tumour characteristics and origin.