Aim The aim of the study was to evaluate the impact of smoking cessation and its timing in the preoperative period on postoperative morbidity in patients undergoing surgery for non-small cell lung cancer (NSCLC). Material and methods Two hundred and eighty-six patients surgically treated for NSCLC were prospectively analyzed in terms of duration and intensity of smoking, time period from smoking cessation to surgery, and postoperative morbidity. The patients were divided into five groups: I – current smokers and past smokers who quit smoking less than 2 weeks before surgery ( n = 67), II – past smokers who quit 2 weeks to 3 months ( n = 106), III – past smokers who quit 3 months to 1 year ( n = 30), IV – past smokers who quit more than 1 year ( n = 71), V – never smokers ( n = 12). Results In the analyzed group 95.8% were smokers or past smokers. Postoperative complications occurred in 40.2% of patients including pulmonary (21.3%) and cardiac morbidity (17.8%). The pulmonary and circulatory morbidity rates were the lowest in group V but the differences were not significant. Similarly, there were no significant differences between groups with and without pulmonary or circulatory complications regarding: number of daily smoked cigarettes, smoking duration and the moment of cessation. The analysis of segmental regression showed the smallest percentage of complications in patients who quit smoking between the 8 th and the 10 th week before the operation. Conclusions Among patients surgically treated for NSCLC, duration of smoking and number of smoked cigarettes has no significant influence on frequency and type of postoperative complications. The best moment to quit smoking is the period between the 8 th and the 10 th week preceding surgery.