Adrenal cysts are very rare lesions, usually asymptomatic or without characteristic symptoms. They are classified as pseudocysts, endothelial cysts, epithelial cysts or parasitic cysts. Although pseudocysts are reported to be the most common clinically recognized adrenal cysts in surgical series, endothelial cysts are more common in autopsy series. We studied 15 consecutive patients with adrenal cysts who underwent surgical resection at our institution from 1990 to 2005. Of 15 patients with adrenal cysts, 10 had pseudocysts, 3 epithelial cysts, 1 an endothelial cyst and 1 a parasitic cyst. In conclusion, a better understanding of cystic adrenal masses is necessary to recognize true adrenal cysts and differentiating them from adrenal carcinoma or adenoma by demonstrating the foci of cystic or degenerative changes. Copyright (c) 2008 S. Karger AG, Basel.