The survival rates of children with chronic conditions have increased markedly over the past decades. Hence, many of them have a fair chance of reaching adulthood thanks to advanced treatment options. However, these patients are in need of life-long specialized care addressing their specific healthcare needs at each respective stage of their life. During adolescence, these patients are expected to transfer their care from the pediatric environment towards an adult-focused setting. To prevent an abrupt and unprepared transfer of care, it is recommended to provide these patients education, counselling and guidance through a transition program. The goal of a transition program is to prepare adolescents for the challenges faced in adulthood and adult healthcare. Although preliminary data suggest that structured transition programs are associated with increased patient satisfaction, self-care, self-advocacy, and psycho-social functioning, high quality studies on the impact of such programs are scarce. The first aim of this study is to develop a prototype of a multidisciplinary transition program for young patients with diabetes type I, asthma or obesity, using an experience-based co-design methodology. Next, the project will evaluate the impact of this program prototype in terms of clinical effectiveness, cost effectiveness and user experiences in adolescents and their families.