The purpose of this study was to examine how body image and satisfaction from it changes according to gender and age, and how it relates to physical activity and self-reported BMI in adolescents. The sample was 496 adolescents (226 boys and 270 girls) aged 13 to 17 years old, attending Gymnasium and Lyceum in rural cities of Greece. The tools used were the Body Image figures scale (Rand & Wright, 1999) and the Leisure Time Exercise Questionnaire (Godin & Shephard, 1985). According to the results, the boys were more satisfied with their body image than girls. This relationship, however, was statistically significant only in Gymnasium (p < .01), where the probability of a girl not being satisfied with her body was 2.82 times higher than a boy’s. In high school, the percentage of adolescents who were not satisfied with their bodies was similar for boys and girls (27.4% and 22.4% respectively). The higher the level of satisfaction with their body image was, the lower the BMI in both age groups, for both sexes (p < .001). Similarly, greater satisfaction with body image was associated with higher levels of physical activity with the exception of high school girls, where higher scores were found in individuals with low body image satisfaction - these differences however, were not statistically significant. It seems that the social stereotypes and standards for slim body, imposed very early in children, cause problems with body image not only in boys but also in girls. Maybe a good structured intervention with physical activity or exercise should positively contribute in improving adolescents’ body image.