My PhD project's overarching research foci is the development and importance of young Norwegian’s leisure in a public health perspective, particularly as it relate to mental health and wellbeing. The project adopts a life-course perspective where the main concern is with youth as a period of transition between childhood and adult roles. It involves exploring 16-19 year olds’ active leisure that make up youth lifestyles, in particular with regard to (i) the mechanisms by which the transition from lower- to upper secondary school affect leisure and sporting outcomes; (ii) the role ‘significant others’ and the interdependencies therein (such as parents, friends and peers) play in the development of youngsters’ leisure lives and (iii) the significance of wider social influences – specifically, class, gender and ethnicity. The study is a mixed-method study that extends a three-year longitudinal research project that followed a cohort of lower secondary school pupils through grade 8-10. This study seeks to build upon that project by carry out qualitative interviews and small-scale quantitative questionnaires on the same cohort during their upper-secondary school period.