Adrenal cysts are rare (0,064%-0,18% in autopsy series) and less than 500 cases have been reported in the western literature. Incidental diagnosis of adrenal cysts, however, is reported with increasing rates. We observed 12 patients with adrenal cyst. Each of them had a careful laboratory and instrumental evaluation; all the patients were operated. In our series about 67% of the patients were symptomatic (6 patients with abdominal pain, 1 with palpable mass, 1 with hemorrhagic shock). No biochemical alteration was observed. Conversely we observed an unusual subclinically hyperfunctioning cystic adenoma, potentially progressive to a clinically recognizable endocrine syndrome. US, CT and MRI had a sensitivity of 66,7%, 80% and 100% respectively. Adrenalectomy was performed in all patients. The pathological findings were: 1 epithelial cyst (cystic adenoma), 2 endothelial cysts (vascular cystic ectasia with adenomatous adrenocortical hyperplasia and 1 vascular cyst) and 9 pseudocysts. On the basis of these results, we conclude that a careful hormonal, morpho-functional and instrumental evaluation is indicated in all adrenal cysts, even if the available diagnostic procedures, even when combined, cannot always define their nature. Surgical excision, when possible by laparoscopic approach, is indicated in presence of symptoms, endocrine abnormalities (even when subclinic), complications, suspicion of malignancy and/or large size (>5 cm). Adrenal gland must be excised en bloc, also because of the possible presence of other adrenal lesions.