BACKGROUND: Effective means of transitioning adolescent patients with chronic illness from paediatric to adult medical care are poorly documented and supported by limited evidence. The purpose of this study is to describe expectations and concerns of adolescents with chronic illness regarding transition from subspecialty paediatric to adult-centred care during the transition process in order guide effective programme design and implementation. METHODS: Qualitative content and thematic analysis of semi-structured individual interviews with 22 adolescents with chronic illness, including cystic fibrosis, sickle cell disease, juvenile rheumatoid arthritis, and inflammatory bowel disease. Interviews took place at 1-3 time points over an 18-month study period. RESULTS: Transition topics included: timing of transfer to adult care, the transition process, attitudes about transition, and factors that might aid transition. During the study period, one-third of participants made the transition to adult-oriented health care. All participants who had transitioned to adult-oriented care reported participating in a structured transition programme. Concerns of those who had not initiated the transition process centred on re-establishing relationships and bringing a new team ‘up to speed’. Most adolescents anticipating transfer to adult care identified only downsides and felt unprepared to transition at the time of the interview. Subjects who had transitioned noted benefits of the adult-oriented system, even if they had been ambivalent prior to transfer of care. Participants suggested that earlier discussions about transition, opportunities to meet new healthcare teams and visits to adult-oriented venues prior to transition might aid in the transition process. CONCLUSIONS: Subspecialty paediatric providers should anticipate common fears and concerns of adolescents and discuss the benefits of transfer to adult-oriented care. Further evaluation of existing transition programmes is an area for future study and is necessary for improvement of the continuum of care for adolescents with chronic medical conditions.