Objective We investigated the efficacy of cilostazol treatment for 2 years against carotid intima media thickness (IMT) progression in type 2 diabetic patients without cardiovascular disease history, as compared with other antiplatelet agents. Methods 217 type 2 diabetic patients who had undergone carotid IMT measurement twice within a 1.5-2.5 year (mean 2.06 ± 0.32 years) interval was recruited. Among these participants, we classified them into three groups according to antiplatelet agent treatment: group 1 (n = 66), antiplatelet naïve; group 2 (n = 75), other antiplatelet agent administration; group 3 (n = 50), cilostazol administration. We then analyzed the changes in clinical characteristics from baseline to year 2. Results The changes in annual mean IMT at year 2 were 0.019 ± 0.045 mm, -0.001 ± 0.058 mm and -0.019 ± 0.043 mm for groups 1, 2 and 3, respectively (P < 0.001). Mean change in total cholesterol, LDL-cholesterol and triglyceride compared with baseline was most decreased in group 3 and it was still significant after adjustment for statin use. Even after adjusting for changes in glucose, LDL cholesterol from baseline, we also observed that the odds ratio of carotid IMT progression was lowest in patients who were treated with cilostazol. When we categorized patients by baseline carotid IMT tertile, the efficacy of cilostazol on carotid IMT reduction was significant only when baseline IMT was over 0.662 mm (mean : 0.801 ± 0.108). Conclusion Two-year treatment with cilostazol strongly inhibited carotid IMT progression than other antiplatelet agents in type 2 diabetic patients without cardiovascular event. This beneficial effect was significant when baseline IMT was over mean 0.801 mm.