Abstract: AIM:To investigate the effect of clopidogrel and cilostazol on platelet aggregation rate (PAR) in patients with type 2 diabetes mellitus (T2DM) and the possible factors that influence their effect. METHODS: There were 1 153 patients with T2DM who were randomly divided into two groups: clopidogrel group (n=576) and cilostazol group (n=577). PAR was detected at baseline and 1 week after medication. PARs were compared between groups and the factors affecting PAR such as lipids, fasting glucose, fasting insulin, glycosylated hemoglobin and dosage of insulin were examined. RESULTS: The changes of PAR before and after medication were (19±17)% in clopidogrel group and (21±14)% in cilostazol group, with no significant difference between groups, suggesting that clopidogrel and cilostazol achieved a similar effect on PAR rate. Low-density lipoprotein and insulin dose were the independent risk factors of clopidogrel resistance, whereas triglycerides and insulin dose were independent risk factors of cilostazol resistance. CONCLUSION: Cilostazol may be superior to clopidogrel in preventing cardio/cerebrovascular events in patients with diabetes.