Background: Previous studies have shown that stenting of small vessel was associated with higher rates of long-term adverse events, especially target vessel revascularization. Objectives: The aim of this study is to assess the short and long-term clinical outcomes according to the vessel size of infarct related artery (IRA) after revascularization with drug-eluting stent (DES) in patients with acute myocardial infarction (MI). Methods: A total of 3,274 patients enrolled in the Korea Acute Myocardial Infarction Registry who underwent only one DES implantation for IRA were grouped according to infarct vessel diameter: group I (small vessel, implanted DES diameter ��� 2.75mm, N=635, male 60.3%) and group II (large vessel (implanted DES diameter >2.75mm, N=2,639, male 77.1%). Patients with multi-vessel or left-main disease were excluded. The primary endpoint was major adverse cardiac events (MACE), including death, MI, and target lesion revascularization at 12 months after percutaneous coronary intervention (PCI). Results: Patients in group I were older (62.4짹12.4 vs. 58.6짹12.5 years, p<0.001); had higher prevalence of diabetes (24.8 vs. 19.8%, p=0.009), hypertension (45.7 vs. 38.5%, p=0.001), and stenotic lesions in the left circumflex coronary artery (28.3 vs. 11.2%, p<0.001); and were more likely to have lower level of maximal troponin-I (37.8짹71.7 vs. 55.9짹112.7 ng/mL, p=0.001). There were no differences between the group in Killip classification, dyslipidemia, lesion characteristics, stent length, pre- and post-PCI Thrombolysis In Myocardial Infarction flow (TIMI). In-hospital mortality was higher in group I (3.0 vs. 1.4%, p=0.012). During follow-up, however, the rates of composite of MACE at 1, 6, 12 months were not statistically between the two groups. In multivariate analysis, Killip class���II (odds ratio (OR), 8.358; 95% confidence interval (CI), 3.109 ~ 22.466; p=<0.001), age>65 years (OR, 4.106; 95% CI, 1.287 ~ 12.094; p=0.017), pre-procedural TIMI flow grade 0 (OR, 2.802; 95% CI, 1.021 ~ 7.693; p=0.045), ejection fraction <40% (OR, 7.042; 95% CI, 2.551 ~ 19.607; p<0.001) were independent predictors of in-hospital mortality . Conclusion: Patients with small vessel infarction had similar angiographic and clinical outcomes, compared to those with large vessel infarction after PCI with DES during a 12-month clinical follow-up.