To identify factors which improve glycaemic control measured as HbA1c in children and adolescents with diabetes treated at paediatric departments.Through data from the Swedish paediatric diabetes quality registry, SWEDIABKIDS, five centres respectively with the lowest, highest, and largest decrease in centre mean HbA1c (Low, High, Decrease HbA1c centres) were identified. Diabetes team members completed questionnaires (109 of 128 responsed) and reported team structure, process and policy. Open-ended questions were analysed with summative content analysis.Compared to the High HbA1c centres, the Low and Decrease HbA1c centres showed higher compliance with guidelines, although they had shorter professional experience and lower proportion of special diabetes-educated team members. A clear message was given and the centres aimed at a lower HbA1c target value. Team members were devoted, had a positive attitude and perception of a well-functioning team. Trends for higher mean insulin dose and larger centre size were found. High HbA1c centres gave a vague message and had a perception of lack of cooperation in the team.Team members’ policy and approaches affect glycaemic control in children and adolescents. Team members need to be aware of their approach and of the importance of using resources within the team.