Diabetes mellitus (DM) is an established risk factor predisposing to male erectile dysfunction (ED), and it has been calculated that more than 50% of diabetic men develop ED within ten years of diagnosis. It has been suggested that the risk of ED increases with metabolic indices of inadequate diabetes control and with a longer duration of disease. Loss of the functional integrity of the endothelium and subsequent endothelial dysfunction plays an integral role in the pathogenesis of diabetic ED. Coronary and peripheral atherosclerosis are frequent complications of DM and diabetic patients have an increased risk of future cardiovascular events comparable to that of patients with coronary artery disease. The prolonged half-life of tadalafil (17.5 hours) and its prolonged period of responsiveness (36-hours), constitute an ideal pharmacokinetic profile for once-a-day dosing and makes it an ideal candidate for rehabilitative therapy in DM patients, whereas a poor compliance with on-demand schedule is reported. The aim of this review will be to give an update on clinical overall efficacy and safety of tadalafil trials, i.e. in diabetic population, and finally provide evidences for redefining the role of chronic treatment in selected group of patients.