Objectives: To characterize a motivational profile of reasons for smoking among teenagers. To investigate the influence of clinical and social elements on observed scores. Methods: High school students who smoked in the past month (n = 226; age, 16.4 +/- 10 years; 46.5% male) answered a questionnaire during school time. The instrument included the University of Sao Paulo Reasons for Smoking Scale (USP-RSS), the Fagerstrom Test for Nicotine Dependence, and clinical and social information. The USP-RSS scores from 307 healthy adult smokers (67.5% male; age, 37.9 +/- 11.2 years) were also used for comparisons. Results: Most of the adolescents (90.2%) exhibited low or very low levels of nicotine addiction (median Fagerstrom Test for Nicotine Dependence score 0, range 0 to 8). The mean scores of the USP-RSS subscales were as follows: Addiction, 1.9 +/- 1.1; Pleasure From Smoking, 3.0 +/- 1.3; Tension Reduction, 2.4 +/- 1.3; Stimulation, 1.9 +/- 0.9; Automatism, 1.3 +/- 0.6; Handling, 2.3 +/- 1.1; Social Smoking, 1.9 +/- 1.0; Weight Control, 1.4 +/- 1.0; and Affiliative Attachment, 1.6 +/- 0.9. In comparison with adults, teenagers exhibited lower scores for Addiction, Pleasure From Smoking, Tension Reduction, Automatism, Weight Control, and Affiliative Attachment and higher scores for Social Smoking (P < 0.05). Older age, past school failure, illicit drugs use, alcohol abuse, high levels of perceived stress, and the death of at least one parent were associated with high scores for all subscales. Conclusions: The USP-RSS subscales Addiction, Pleasure From Smoking, and Social Smoking were important factors for adolescent smoking. Comparisons with adult smokers stressed the importance of the component of Social Smoking. The identification of distinctive factors that drive teenagers to smoke might help in making decisions dealing with interventions aimed at smoking cessation and control.