Without treatment, Cushing's disease has significant morbidity and mortality. Where a surgical approach may not be feasible, or is refused by the patient, medical therapy becomes the only option. In this case report, we discuss the effects of two years of ketoconazole treatment on diabetes regulation and insulin resistance in a patient reluctant to agree to surgery. A 62 year-old female patient with uncontrolled type 2 diabetes mellitus was investigated. Cushing's disease was confirmed by the results of high urine free cortisol level and dexamethasone suppression tests.