Tobacco dependence is a complex phenomenon in which physical and psychological components go hand in hand, and it is often considered as one of the major barriers to quit smoking. However, we still need to increase our understanding of the processes through which tobacco dependence relates to smoking cessation. This research aimed to investigating whether changes in smoker versus ex-smoker (abstainer) self-concept account for the association between tobacco dependence and successful smoking cessation. We used longitudinal data drawn from the evaluation of a smoking cessation intervention. A sample of smokers enrolled in the program filled in a questionnaire at the beginning of the intervention (baseline: N = 779), 6 months later (i.e., at the end of the intervention: T1, N = 532), and 9 months later (T2; N = 387). We assessed tobacco dependence (baseline), smoker versus ex-smoker self-concept (baseline, T1, and T2) and smoking status (baseline, T1 and T2). Tobacco dependence was negatively associated with smoking cessation maintenance, and this effect was mediated by changes in self-concept: The greater tobacco dependence, the lower the likelihood that former smokers develop an ex-smoker self-concept during the program, which results in relapse at T1 or T2. Successful smoking cessation interventions should provide strategies preventing the negative effects of tobacco dependence on identity transition.