Young people with chronic physical illness are required to develop self-management skills in order to maintain optimal physical health as they transition into adult care. It is often during this vulnerable transition period that deterioration in illness control and unplanned hospitalisations are seen as a result of inadequate self-management. Mobile technology has been proposed as an innovative opportunity to improve the management of chronic illnesses as young people transition to adult care. To date, there appears to be limited empirical evidence about the use of mobile phone applications aimed at supporting self-management in adolescents living with chronic illnesses and the available applications are disease-specific. Four studies were conducted in this thesis: 1) a systematic review of mobile and web-based applications that support self- management and transition in young people with chronic illness; 2) a narrative review of mobile applications that support self-management in young people with chronic illness as identified in the systematic review; 3) the development of TransitionMate (a generic application to support transition in young people with chronic illness) research protocol; 4) the refinement of the TransitionMate application and the recruitment process for the TransitionMate study. The systematic review found that there are still limited data about the effectiveness of applications facilitating the transition of adolescents with chronic illness from paediatric to adult health care. Features between the different applications presented in the systematic review showed similarities supporting the concept of developing a generic, not disease specific, application which can be easily tailored through simple modifications to support the users' need. The narrative review supports the evidence that young people have expressed satisfaction in integrating the use of applications as a self-management tool, but that empirical data to support their long-term engagement with an application are not available. TransitionMate is a generic application developed in a clinical research environment to support young people with chronic illness in their transition process. Comments, concerns, recommendations and reactions about the recruitment process and the TransitionMate application are also presented.