male gender

signed written consent form

type 2 diabetes mellitus diagnosed within 5 years before enrolment in the study

body mass index (bmi) < 35

ed (severe, moderate or light according to the international index of erectile function - erectile function domain score < 26 (rosen et al. 1997))

age range: 40-65 years.

systemic diseases except type 2 diabetes mellitus

absence of ed

psychiatric disorders

all contraindications to treatment with pde5 inhibitors, such as retinitis pigmentosa, non-arteritic anterior ischaemic optic neuropathy, history of coronary artery disease, recent myocardial infarction, unstable angina, systemic arterial hypotension, nitric-oxide donors therapy, severe hepatic and renal failure.