Background and Objectives:Tobacco smoke contains many substances that are harmful and induce cancerogenesis. Carbon monoxide (CO) is the parameter commonly monitored by smoking cessation centres. The purpose of this study was to analyse other parameters and risk factors, including respiratory function and CEA (serum carcinoembryonic antigen) levels, in patients undergoing smoking cessation. Methods:One hundred and eighty current smoking patients current smokers were recruited from the outpatients for smoking cessation. Sociodemographic and lifestyle analyses were performed on them. They were also studied for respiratory function parameters and CEA (serum carcinoembryonic antigen) levels. A control group of 171 former smoking patients were also studied for functional and clinical parameters. Current smokers were also monitored for several parameters in the first 3 months after starting therapy with nicotine inhaler and varenicline, in addition to the behaviour therapy. Results:Some functional and clinical differences were found between the smokers and the former smokers groups. In the smokers' group we found no significant differences in sociodemographic and lifestyle between females and males. Regarding the response to varenicline-nicotine treatment combined with minimal advice, 56% of patients stopped smoking after 3 months of therapy; 30% of these had a level of severe bronchial obstruction. Operating parameters and the level of CEA at the beginning of the therapy were evaluated after 3 months, showing significant differences. Carboxyhemoglobin was reduced by 1.06%, oxyhemoglobin increased by 2.94%, FEF 25/75% increased by 16%. Conclusions:We can say that smoking cessation leads quickly to the improvement of clinical, functional and laboratory parameters. Patients with severe obstruction are more motivated to stop smoking.