Introduction: This study applied a cost-benefit analysis from a societal viewpoint to evaluate the Outpatient Smoking Cessation Services (OSCS) program. Methods: The costs measured in this study include the cost to the health sector, non-health sectors, the patients and their family, as well as the loss of productivity as a result of smoking. The benefits measured the medical costs savings and the earnings due to the increased life expectancy of a person that has stopped smoking for 15 years. Data were obtained from the primary data of a telephone survey, the literatures and reports from the Outpatient Smoking Cessation Management Center and government. Sensitivity analyses were conducted to verify the robustness of the results. Results: There were 169,761 cases that participated in the outpatient smoking cessation program in the years 2007 and 2008, of those cases, 8,282 successfully stopped smoking. The total cost of the OSCS program was 18 million USD. The total benefits of the program were 215 million USD with a 3% discount rate; the net benefit to society was 196 million USD. After conducting sensitivity analyses on the different abstinence, relapse, and discount rates, from a societal perspective, the benefits still far exceeded the costs, while from a health care perspective, there was only a net benefit when the respondent's abstinence rate was used. Conclusions: From a societal perspective, the OSCS program in Taiwan is cost-beneficial. This study provides partial support for the policy makers to increase the budget and expand the OSCS program.