The study examines the impact of body image in adolescents' well-being. Well-being was assessed with the scale Kidscreen10, with the Cantril ladder for satisfaction with life and with an ad hoc happiness scale. The study presents data on adolescent health from the Health Behavior in School-aged Children (HBSC)/World Health Organization study in Portugal (2006), with a sample of 4,877 adolescents, average age of 14 years old and gender distribution at 49,6% males. Portuguese adolescents showed differences between gender and age group regarding their body image-related satisfaction/dissatisfaction and self-perceived body image, being that both components have a direct impact on the levels of well-being. The male gender has better results in the perception of body image and, consequently, well-being. The largest inter-gender differences for well-being is at 15 years of age. The main predictors of well-being are the look and body satisfaction/dissatisfaction, with greater importance on the affective component. This research highlights the importance of body image for adolescents' well-being, as well as to prepare educational strategies adapted to adolescents' age and gender, by helping them to develop skills concerning self-knowledge and caring for their look.