The widespread use of ultrasonography and computed tomography has resulted in an increased diagnosis of large sized adrenal cysts with diameters of more than 5 cm. Most of these adrenal cystic lesions are clinically silent and are therefore often diagnosed incidentally. Since up to 7% of adrenal cysts are malignant, a careful hormonal, morpho-functional and instrumental evaluation is mandatory. In particular, functioning adrenal carcinomas or pheochromocytomas have to be ruled out. Fine needle aspiration cytology as well as examination of a punch biopsy specimen of the cystic wall are of limited value, as there is considerable overlap in cytologic and histologic features of benign and malignant adrenal cystic lesions. Immediate surgical excision is indicated in the presence of symptoms, suspicion of malignancy, increase in the size or detection of a functioning adrenal cyst. En bloc adrenalectomy, preferably by a laparoscopic approach, has become the treatment of choice.