Nicotine addiction is the most common type of addiction and one of the leading causes of diseases that can be prevented by smoking cessation, which is now considered a process rather than a separate event. In understanding the process of smoking cessation, increasingly used transtheoretical model (TTM) of health behavior change, which observes this process through stages (precontemplation, contemplation, preparation, action and maintenance) depending on the willingness to change behavior. The objectives of this study are: to examine the role of emotion regulation strategies, stages of change, perception of pros and cons of change, and self-efficacy in the severity of nicotine dependence; compare smokers and non-smokers according to emotion regulation strategies and defeatist beliefs. Contribution of predictors (sociodemographic characteristics, regulation strategies, perceptions of pros/con, self-efficacy and defeatist beliefs) were examined in prediction of nicotine addiction severity. Data were collected by the ‘snowball’ method. Participants were contacted by posting an invitation to participate in the research on social media. The study involver 365 participants (433 woman and 202 men) of whome 331 non-smokers and 304 smokers in different stages of change (those who actually smoke, those who guit smoking within six months and are in the action stage, and those who stopped smoking more than six months ago and are in the maintenance phase). The research used instruments: emotion regulation questionnaire, decision balance balance questionnaire, self-efficacy questionnaire in smoking cessation, Fagerstrom nicotine addiction questionnaire, subscale of defeatist beliefs that is part of the scale of dysfunctional beliefs.Statistical analyzes showed smokers and non-smokers did not differ in their propensity to use emotion regulation strategies cognitive reassessment and suppression. Results showed significant difference between smokers and non-smokers in defeatist beliefs – smokers showed more defeatist beliefs. There have been significant differences in the perception of the advantages and disadvantages of change through the stages of the change process as well as differences in self-efficacy with respect to stage - self-efficacy increases with the ‘higher stages’ of the change process. No difference in defeatist beliefs was found with respect to the severity of the addiction or with respect to the stage of change. The presumed predictors of the severity of nicotine addiction did not prove significant, nor did the moderating effect of defeatist beliefs. Variables: perception of the advantages and disadvantages (pros and cons) of behavior change, self-efficacy (within the transtheoretical model of behavior change), and especially defeatist beliefs are related to smoking and interesting variables for further research.