Background: Between 1998-2009 South Korea experienced significant progress in reducing the male smoking rate from 66.3% to 46.9%. As part of a significant government effort in the area of smoking cessation intervention, the Korean government implemented the national "Smoking Cessation Clinics (SCC)" program in 2004. Materials and Methods: Data covered 804,334 adult male smokers participating in SCC program at 253 public health centers between 2006-2009. We examined participant cessation rates with the SCC program, their characteristics and program intervention components using health insurance status as a socioeconomic status (SES) indicator. Multivariate logistic regression analyses were performed correcting for intra-class correlations within public health centers. Results: The overall 6-month quit rate was high (46.8%). Higher odds of smoking cessation were positively associated with higher levels of behavioral counseling sessions, but not nicotine replacement therapy (NRT). Cessation rates were lower for Medicaid participants than for regular health insurance participants. Disadvantaged younger smokers were less likely to participate in the program. Older smokers were more likely to quit regardless of SES. Stress was cited as major reason for failure. Conclusions: SES inequalities across different age groups exist in smoking cessation among Korean adult male smokers. There is a need for intervention programs specifically targeting sub-populations of SES by different age groups.