OBJECTIVES: To assess the effectiveness and costs of the Smoking Cessation Program (SCP) in the Public Unified Health System (SUS) and to estimate the cost for its full implementation in the city of Goiânia, Brazil. METHODS: The SCP intervention targets group of smokers, and includes medical visits, cognitive-behavioral group therapy, and medication use, lasting six months. Costs for SCP intervention and management were estimated. The SCP full implementation was defined as the program's expansion to meet the demand of all smokers motivated to quit smoking in the city of Goiânia. Direct medical and non-medical direct costs were considered, including staff, medications, consumables, general expenses, transportation, travel, events and capital costs. Microcosting and activity-based costing methods were used. Cost for the federal, state and municipal levels were estimated. The SUS perspective was considered. Two-way sensitivity analysis was conducted. Data sources included a convenience sample of primary health facilities, municipal and state health departments, and the Ministry of Health. Costs were estimated in Reais (R$) and U.S. Dollars (USD), considering the exchange rate of December/2010, which was 1.67. Quitting rates were estimated as the percentage of patients who reported not smoking at the end of the intervention. Costs of the SCP are presented as total cost of the intervention; costs stratified by component and level of funding source; cost per patient; and cost per quitter. RESULTS: The average quitting rate was 37.2%. The cost of SCP in Goiânia was R$428,580 (US$257,220), of which 23% were program management costs. Cost per patient was R$534 (US$320) and cost per quitter was R$1,433 (US$860). The SCP´s full implementation reaching the estimated 37,455 smokers in Goiânia motivated to quit would cost R$21.5 million (US$13). CONCLUSIONS: The SCP is highly effective. Additional efficiency could be gained by expanding patient's access to the program.