We present a patient with a rare cause of ectopic ACTH-dependent Cushing's syndrome, caused by a pheochromocytoma. The case provides clues for a detailed discussion on the pitfalls and diagnostic difficulties in establishing the correct underlying cause of ACTH-dependent Cushing's syndrome. It clearly demonstrates that the relative contributions of clinical, biochemical, and radiological clues in establishing the correct underlying cause of Cushing's syndrome may differ considerably between Cushing's disease and Cushing's syndrome due to ectopic overproduction of ACTH. In addition, the literature concerning ACTH-producing pheochromocytomas is reviewed.