BackgroundIn recent years, the prevalence of daily smokers has decreased in all developed countries due to a great variety of factors. Despite this decrease, the effectiveness of clinical treatments has decreased and several studies report a change in smokers’ characteristics. The purpose of the present study is to analyze the changes in the characteristics of Spanish smokers who seek smoking cessation treatment between 2001 and 2010 and the changes in the effectiveness of such treatment.MethodsThe sample was made up of 870 smokers who sought psychological treatment for giving up smoking at the Smoking Cessation Unit in the Faculty of Psychology of the University of Santiago de Compostela (Spain) during the period 2001 to 2010.ResultsSmokers in the 2006–2010 group, compared to those in the 2001–2005 group, were older, smoked fewer cigarettes per day and of a brand with fewer mg/nicotine, had been smoking longer, were less motivated to give up smoking, and had more antecedents of depression. Quit rates were validated by testing smokers' carbon monoxide (CO) levels.Percentages of abstinence were higher in the 2001–2005 group than in the 2006–2010 group (58.7% vs. 52.15 at the end of treatment, p = 0.05); 30.8% vs. 24.2% at 6 months follow-up, p = 0.031; 27.5% vs. 22% at 12 months follow-up, p = 0.059). Although abstinence decreased more than 5% in the 2006–2010 group there were no differences between the two groups in nicotine dependence. Those participants who did not assist to the follow-up were considered smokers at pretreatment level.ConclusionsIn Spain there has been a qualitative change in the profile of the smokers seeking smoking cessation treatment. Treatment effectiveness has decreased, and the variables predicting intervention outcome have changed.