The present research aims to characterize the Health- Related Quality of Life (HRQoL) of children and adolescents and to analyze the HRQoL by gender, age, socioeconomic status (SES), nationality and health condition. The HRQoL will be assessed by analyzing the children's and the adolescents' perception of their own HRQoL, by considering the parents' perception of their children's HRQoL and finally by considering the education professionals' perception of children' and adolescents' HRQoL; and to identify the personal and social factors associated to the HRQoL promotion in children and adolescents by the characterization of children' and adolescents' sense of self, their life orientation, their social support satisfaction and their health related behaviours.