A 47-year-old man with Cushingoid appearance was admitted to our hospital showing excessive secretion of cortisol at intervals of a few days. Cyclic Cushing's disease was confirmed. Two years earlier, results of hormonal assessment had been within normal limits and macroadenoma had been incidentally detected in the pituitary. Dexamethasone suppression testing revealed various responses and a small lung tumor was detected, therefore his condition was misinterpreted as ectopic ACTH-producing tumor or pituitary cyclical Cushing's disease, leading to lung resection that confirmed cryptococcal pneumonia. The pituitary tumor was finally identified as the cause of cyclic Cushing's syndrome and fully removed, allowing remission.