A 70-year-old woman was referred to the authors' unit following hospitalization for cardiac failure, high urinary free cortisol concentrations and severe hypokaliemia. A computed tomography scan of the abdomen showed an adrenal adenoma. The 24-hour urinary free cortisol values were high and plasma cortisol levels failed to suppress following 1 mg dexamethasone test. Aldosterone to plasma renin activity ratio was also pathologic, confirmed by saline load. She showed no symptoms of glucocorticoid excess. She was diagnosed with combined primary hyperaldosteronism and Cushing's syndrome. Cases of adrenal incidentalomas co-secreting cortisol and aldosterone are rare; they should be addressed in patients undergoing adrenal surgery for Conn's syndrome to avoid adrenal insufficiency after removal of the tumor.