Purpose: The purpose of this study was to identify factors influencing adolescent smoking behavior in the Seoul area. Method: A total of 6.352 middle and high school students living in the Gangnam district of Seoul participated in the study. A self report survey method was used to identify factors related to smoking. Result: A stepwise logistic regression analysis identified four factors associated with adolescent smoking: living with a parent who smokes (OR=1.4), having friend (s) who smoke (OR=14.8), negative attitudes toward passive smoking(OR=4.8), and ignorance of the impact of smoking on health(OR=4.6). Conclusion: Based on the study results, components of effective programs to reduce adolescent smoking rates should include programs to deal with peer pressure to smoke and to reduce the impact of parents who smoke, to increase knowledge of the impact of smoking, and to promote positive attitudes toward anti smoking.