Purpose: The purpose of this study was to investigate the patterns of smoking relapse and to identify risk factors related to smoking relapse among those successful in smoking cessation at the smoking cessation clinics of public health centers. Methods: Data were collected from 1,705 six-month quitters and analyzed by the Kaplan-Meier analysis and the Cox proportional hazard model. Results: The rate of smoking relapse was 38.2% in 1 year, 44.4% in 2 years, and 47.8% in 5 years. The vast majority of relapse (62.3%) occurred within the first six months after quitting. The risk factors related to smoking relapse were age (HR 1.964: 95% CI 1.545, to 2.497), nicotine dependence (HR 1.293: 95% CI 1.087 to 1.539), problem drinking (HR 1.497: 95% CI 1.116 to 2.008), behavioral therapy type (HR 1.398: 95% CI 1.193 to 1.638), and nicotine replacement therapy type (HR 1.363: 95% CI 1.077 to 1.724). Conclusion: For reducing smoking relapse, it is necessary to develop a smoking relapse prevention program for the first six months after quitting and to strengthen behavioral therapy in the course of smoking cessations clinics.