Primary care centers can play a very important role in helping people to stop smoking. There is a large body of research on the effectiveness of specific interventions especially addressed to people who want to stop smoking. In addition to that, there are no studies with a large sample of individuals included that tested the complete range of interventions recommended nowadays for helping people in the different smoking cessation stages of change and with different degrees of physical and psychological dependence, especially including motivational interviewing in those not interested in cessation in the very next weeks. This study will test a complex intervention that at first classifies smokers in stages and after that treats every smoker according to what stage he/she is in at the moment, his/her degree of dependence and his/her own characteristics.