This study examined environmental preferences for adolescent patients in hospital patient rooms and activity rooms to determine age-appropriate healing design elements. The health-related quality of life (HRQOL) concept was adapted to this study as a theoretical framework. In order to develop an age-appropriate healing design, a comprehensive understanding of adolescents‘ cognitive developmental stages and their expectations in hospital settings needs to be recognized. Thirty-two adolescent outpatients aged 15 to 18 participated in the survey. Data collection consisted of three different instruments: Emotional state survey with demographics, Photo analysis with semantic differentials, and environmental preference value survey. Comfort, sadness and stress affected adolescent patients‘ preference responses. Adolescent patients preferred having a home-like environment for their patient rooms due to their needs for comfort and control of privacy. They also preferred having enjoyable and controllable activity rooms that supported peer connection, self-identity, and stress reduction. Environmental values that are important to adolescents were control of privacy, a quiet place to go, a place for activity, and having a controllable outside view.