Diabetes mellitus is characterized by accumulation of risk factors of atherosclerosis, high incidence of metabolic syndrome accompanied with endothelial dysfunction. Diseases of the heart are more common in diabetics as in non-diabetic patients and are divided in these patients into atherosclerotic coronary disease, cardiomyopathy and autonomic neuropathy. There is higher risk of silent myocardial ischemia in these patients. Basal diagnostic procedure is resting ecg (performed at least 1-time a year), exercise-test, echocardiography, respectively thalium-scintigraphy. Diabetic patient must be on very good glucose control, with normal blood pressure, with normal values of LDL cholesterol. Therapy with ACE inhibitors and acetylsalicylic acid is highly recommended.