Patients with type 2 diabetes mellitus have increased risk of cardiovascular disease. Epidemiological studies have shown a correlation between diet and incidence of coronary heart disease. The aim of the study is to determine the effect of a traditional Greek Mediterranean diet on platelet aggregation induced by ADP, arachidonic acid (AA), and especially platelet-activating factor (PAF) on patients with type 2 diabetes mellitus as well as on healthy volunteers. The patients were randomized into two subgroups, A and B. The lipid extracts from traditional Greek Mediterranean-type meals were tested in in vivo for their ability to reduce PAF- or thrombin-induced platelet aggregation. The meals with the most potent anti-aggregating activity were chosen for the diet of both subgroup A and healthy subjects and consumed for a period of 28 days, whereas subgroup B kept to their regular diet that was followed before entering the study. Platelet-rich plasma was isolated before and after the diet, and the ability of platelets to aggregate under the aggregating factors was tested. One-month consumption of diet resulted in a significant reduction in PAF- and ADP-induced aggregation of platelets in both groups of healthy volunteers (PAF and ADP, P < .05) and subgroup A (PAF, P < .001; ADP, P < .05), whereas the AA-induced aggregation was not affected. No effect was observed in subgroup B, which followed the standard diet. Thus the consumption of a traditional Greek Mediterranean diet even for a short period can reduce platelet activity in patients suffering from type 2 diabetes mellitus and in healthy subjects.