Background: Platelet reactivity is enhanced in diabetic patients compared with non-diabetic patients. Several studies demonstrated that triple anti-platelet therapy could produce more potent inhibition of platelet aggregation. Whether this enhanced effect can be maintained in diabetic patients is not well known. Methods: Sixty type 2 diabetic patients were prospectively randomized to double (aspirin, clopidogrel) or triple (aspirin, clopidogrel, cilostazol) anti-platelet therapy after drug eluting stent (DES) implantation. Platelet function parameters included adenosine diphosphate (ADP) 20 and 5 關mol/L induced maximal platelet aggregation (MPA) and late platelet aggregation (LPA) at pre-discharge and 30 days after randomization using light transmittance aggregometry. Results: ADP 20 關mol/L induced MPA at 30 days was significantly reduced in the triple group compared with the double group (p=0.044; primary end point) (Figure). All other platelet aggregation parameter at 30 days was significantly reduced in the triple group compared with the double group. Pre-discharge aggregation parameter tended to be lower in the triple group compared with the double group. Conclusion: Triple anti-platelet therapy resulted in enhanced anti-platelet effects compared with double anti-platelet therapy in type 2 diabetic patients undergoing DES implantation. Keyword: Diabetes, Antiplatelet drugs, Platelet aggregation