BACKGROUND Lung cancer is the leading cause of death from cancer in Germany. 90% of cases are due to the inhalation of tobacco smoke. About 40% of patients with newly diagnosed lung cancer are still smokers. A structured smoking cessation program is medically reasonable in this situation but is only rarely offered. METHODS This review is based on a selective search in the PubMed database combined with a manual search for current publications. RESULTS Many cross-sectional and longitudinal studies have shown that patients with lung cancer benefit from smoking cessation. After resection with curative intent, second tumors are 2.3 times more common, and recurrent tumors 1.9 times more common, in patients who continue to smoke than in those who stop. The overall mortality in smokers is 2.9 times higher. Smoking cessation also lowers the rate of radiation pneumonitis and infection during radiotherapy and prolongs the median survival after chemoradiotherapy for small-cell lung cancer (18.0 vs. 13.6 months). For patients with non-small-cell lung cancer, smoking cessation is associated with a better general state of health (77.5% vs. 57.6%). For the many patients with lung cancer who are treated palliatively, smoking cessation offers the advantages of improved pulmonary function, weight gain, and better overall quality of life. CONCLUSION Smoking cessation in patients with lung cancer is an important means of increasing the efficacy of treatment and improving their quality of life.