Objective: To investigate the processes of change, demographic, health- and smoking-related predictors of both smoking cessation and smoking reduction in adolescents. Methods: Data were drawn from a sample of 755 adolescent smokers who participated in a study testing the efficacy of a text messaging-based intervention for smoking cessation. Demographic, health- and smoking-related variables were assessed at baseline. Five processes of smoking cessation, derived from the Transtheoretical Model and the Social Cognitive Theory, as well as outcome measures were assessed at 6-month follow up. Univariate and multivariate regression analyses were conducted to identify baseline and process variables to predict smoking abstinence and smoking reduction. Results: Male gender (OR = 0.43, p < .01), lower alcohol consumption (OR = 0.90, p = .05) and a lower number of cigarettes smoked per day at baseline (OR = 0.87, p <.01) predicted smoking abstinence. Baseline physical activity predicted smoking reduction (OR = 1.04, p = .03). None of the examined process variables significantly predicted smoking abstinence. The process variable "counter-conditioning" predicted smoking reduction (OR = 1.46, p = .03). Conclusions: Baseline predictors of smoking cessation differ from predictors of smoking reduction. Dynamic or modifiable variables play an important role in predicting adolescent smoking cessation. Practice implications: Counter-conditioning might be an important element in adolescent smoking cessation interventions. (C) 2014 Elsevier Ireland Ltd. All rights reserved.