The study involved 2,101 adolescents, aged 10–18 years, from 21 centres in 17 countries in Europe, Japan and North America. Adolescent quality of life (QOL) was assessed by a previously developed Diabetes Quality of Life Questionnaire for adolescents (DQOL), measuring impact of diabetes, worries about diabetes, satisfaction with life and health perception. Parents and health professionals assessed ‘family burden’ using newly constructed questionnaires. Mean HbA<sub>1c</sub> was 8.7% (range 4.8–17.4%). Lower HbA<sub>1c</sub> was associated with lower impact (p < 0.0001), fewer worries (p < 0.05), greater satisfaction (p < 0.0001) and better health perception (p < 0.0001) for adolescents. Girls showed increased worries (p < 0.01), less satisfaction and poorer health perception (p < 0.01) earlier than boys. Parent and health professional perceptions of burden decreased with age of adolescent (p < 0.0001). Lower HbA<sub>1c</sub> was significantly associated with better adolescent-rated QOL on all four subscales and with lower perceived family burden as assessed by parents and health professionals.