Background and Objective: To assess the cessation and relapse rates of smoking, and analyze the associated variables in a 12-month follow-up study at a smoking cessation unit., Subjects and Method: Patients from the Area de Salud 19 of the Conselleria de Sanitat of the Generalitat Valenciana, coming to a smoking cessation unit., Variables: sociodemographic, smoking habits, smoking social context, psychiatric or medical problems, use of other substances, and treatment. Treatment was administered either individually or in group, and with or without pharmacological support. Type of pharmacological treatment: nicotine replacement therapy and/or bupropion. Evaluation of smoking cessation and relapse: at the end of the treatment, and at follow-up months 1, 3, 6, 9, and 12. Criteria to accept cessation were: it had to be uninterrupted, referred as such by the patient and corroborated by relatives or other witnesses, and supported by a co-oxymetry level < or = 6 ppm., Statistical Analyses: description of quantitative and qualitative variables, evaluation of the relationship between relapse rate and follow-up time when it happens by means of Kaplan-Meier curves, Cox regression, construction of curves of prediction of cessation for subjects with different patterns in the independent variables, and estimations of risk of relapse between any 2 subjects, according to those patterns., Results: 255 subjects (46.7% males); 41.8 (10.8) years of mean age (standard deviation); 25 years of mean duration of the smoking habit; a mean of 2 to 3 previous attempts of cessation smoking, mean duration of the longest period of cessation 6 to 7 months; smoking habit 26.5 (12.1) mean of cigarrettes per day, the average nicotine dependency was moderate, and the average co-oxymetry levels high. Of all the subjects included, 53.3% received single therapy (60% together with pharmacological treatment) and 46.7% had group therapy (18.4% also with pharmacological treatment). Pharmacological treatment was 14.9% nicotine replacement therapy, 17.3% bupropion, and 7.1% both. At the end of the treatment, 42.7% of the subjects kept smoking and, at the end of the follow-up period only 11.4% remained abstinent. Median cessation extent was one month. VARIABLES associated to the extent of the cessation: type of therapy (individual or in a group), pharmacological support, and previous daily amount of cigarrette consume., Conclusions: There were high relapse rates, that depended on the previous amount of consume and on the treatment applied. Both group therapy and pharmacological treatment are significantly useful in order to obtain the best results in long-term cessation rates.