This presentation will focus on a national level Swedish project aimed at examining adolescent athletes’ transition to, and adaptation at, national elite sport schools (NESS). In this study transitional issues (e.g., demands, resources, coping strategies related to sport, studies and private life) and athletes’ personal attributes (e.g., athletic and student identities) were addressed from a holistic lifespan perspective using longitudinal mix-method (quantitative and qualitative) research design. The instruments used in the two quantitative measurements (autumn and spring) included:  the Dual Career Survey (Engström & Stambulova, 2010), the Athletic Identity Measurement Scale (Brewer, Van Raalte, & Linder, 1993), the Student Identity Measurement Scale (Engström & Stambulova, 2010), the Task & Ego Orientation in Sport Questionnaire (Duda, 1989), and the Basic Needs Satisfaction Scale (Chen et al., in press). Participants (main sample) were athletes of 15-16 years old, representing two genders, 27 sports, and 33 NESSs across the country with 261 who took part in the first measurement and 250 who took part in the second measurement. In addition, in-depth interviews were conducted twice a year with 10 participants from the main sample. The results confirmed that starting at NESS meant for student-athletes entering a complicated transition embracing all major spheres of their life. At the beginning of the year the participants underestimated demands of studying, doing sports and living at NESS and overestimated (based on previous relevant experiences) their readiness to pursue dual career at NESS. Later, during the year more awareness and understanding of the reality came, and led to their self-re-evaluation of the adaptation process and outcomes.  So, the 1^st year at NESS can be seen as a way from an illusory to real adaptation (which continued even in the end of the year). Results confirmed that one of the most difficult aspects in the adaptation process at NESS was finding an optimal balance between sport and studies. It appeared impossible all the time to give 100% in both. Therefore, student-athletes had to prioritize one side that typically was sport. Some athletes experienced a dissonance between prioritizing sport and receiving a message from coaches/teachers that they are expected to prioritize studies. The study also showed contributions of athletes’ personal development (e.g., athletic identity, task orientation) to the adaptation process. Moreover, perceived total importance of sport, studies, and private life as well as satisfaction with these life domains contributed positively to student-athletes’ adaptation at NESS.