Background: There has been continuous debate on the phenomenon of ���smoker���s paradox���. Because age can be a major confounding factor, we evaluated the ���smoker���s paradox��� in young adults in Korea Acute Myocardial Infarction Registry (KAMIR). Methods: Among the 6648 eligible patients (pts) with acute myocardial infarction (AMI), 688 pts (572 smokers and 116 non-smokers) were ��� 45 years old. The impact of current smoking on mid-term clinical outcomes was evaluated. Results: Multivariate analysis in the over all study population showed current smoking was an independent predictor for the occurrence of AMI in younger pts [odd ratio (OR) 3.54, 95% confidence interval (CI) 2.66 to 4.72, P=0.014]. Although smokers and nonsmokers had similar clinical outcomes in the overall study population, young smokers paradoxically showed better clinical outcomes than non-smokers at 8 months with lower incidence of cardiac death (0.5% vs 3.4%, P=0.018), total death (0.9% vs 3.4%, P=0.049) and total MACE (5.2% vs 12.1%, P=0.006). Multivariate analysis showed current smoking was an independent predictor for lower incidence of total MACE (OR 0.41, 95% CI 0.20 to 0.84, P=0.014) at 8 months in young AMI pts. Subgroup analysis in young AMI pts receiving percutaneous coronary intervention (PCI) also showed current smoking was an independent predictor of lower incidence of total MACE (OR 0.44, 95% CI 0.20 to 0.98, P=0.046) at 8 months. Conclusions: Despite current smoking paradoxically appears to be associated with better clinical outcomes in younger pts with AMI, intensive smoking cessation efforts still should be emphasized to prevent the early occurrence of AMI.