In our Department arrives a 75-year-old patient with hypertension, diabetes mellitus (DM) treated with hypoglycaemic drugs, dyslipidaemia and ischaemic heart disease post-acute myocardial infarction treated with triple coronary artery bypass surgery and subsequent percutaneous transluminal coronary angioplasty (PTCA). After a new PTCA and positioning of medical stent he is discharged with a double antiplatelet therapy. But after one month two thrombotic events occur in this patients almost simultaneously. Antiplatelet therapy such as clopidogrel and aspirin in combination, is the current gold standard for reducing cardiovascular events in patients with DM, providing a synergistic platelet inhibition through different platelet activation pathways, but platelets of DM patients are characterised by disregulation of several signalling pathways which may play a role not only in the higher risk of developing cardiovascular events and the worse outcome, but also in the larger proportion of DM patients with inadequate response to antiplatelet drugs compared to non DM subjects.