Background: Clinical events including stent thrombosis (ST) after coronary stenting has been associated with platelet inhibition after dual antiplatelet therapy. Recent studies have demonstrated that Asian population may have the lower rate of ST. There might be ethnic difference in various factors, and the different response to clopidogrel according to ethnicity can be a cause of this phenomenon. Methods: We enrolled Asian patients treated with coronary stenting and receiving chronic clopidogrel therapy (��� 1 month) (n = 239). Platelet reactivity (PR) was assessed with conventional aggregometry and VerifyNow assay. High post-clopidogrel platelet reactivity (HPPR) was defined 5umol/l ADP-induced PR ��� 50%. Results: Patients showed relatively higher post-clopidogrel residual PR. PRs after 5 and 20 umol/l ADP stimuli were 44.1 짹 16.6% and 57.3 짹 16.2%, respectively, and the rate of HPPR was 38.1%. The mean value of P2Y12 reaction unit (PRU) was 252 짹 78, and 57.7% of all cohorts showed PRU ��� 240. Cut-off points of highest quartile were 58%, 70% and 305 in terms of 5 and 20 umol/l ADP-induced PRs, and PRU. PR with 5umol/l ADP stimuli were significantly higher in female (50.1 짹 15.4% vs. 41.8 짹 16.2%, P < 0.001). Conclusions: Asian patients with coronary stenting show reduced response to clopidogrel and a high rate of HPPR, which may be related with a higher prevalence of the cytochrome 2C19 polymorphism in Asian population. Because there is a discrepancy between clinical outcomes and response to clopidogrel, further studies will be needed to find out the underlying mechanism of ethnic difference in occurrence of clinical events after coronary stenting.