Objectives: To develop and evaluate a child-centred patient decision aid for young-people, and their parents, supporting shared decision making about fixed orthodontic appliance treatment with dental health professionals, namely the Fixed Appliance Decision Aid (FADA). Methods:The studies were undertaken in a UK teaching dental hospital orthodontic department in 2013-14.The development phase involved an interview study with: a) 10 patients (12-16 years old), and their parents, receiving orthodontic care to investigate treatment decision making and inform the content of the FADA and b) 23 stakeholders critiquing the draft decision aid's content, structure and utility. The evaluation phase employed a pre-/post-test study design, with 30 patients (12-16 years old) and 30 parents. Outcomes included the Decisional Conflict Scale; measures of orthodontic treatment expectations and knowledge.Results: Qualitative analysis identified two informational needs: effectiveness of treatment on orthodontic outcomes and treatment consequences for patients' lives. Quantitative analysis found decisional conflict reduced in both patients (mean difference -12.3, sd 15.3, 95% CI 6.6 to 17.9; p<0.001) and parents (mean difference -8.6, sd 16.6, 95% CI 2.5 to 14.8; p=0.002); knowledge about duration and frequency of orthodontic treatment increased; expectations about care were unchanged. Conclusions:Using the FADA may enable dental professionals to support patients and their parents, decisions about fixed appliance treatments more effectively, ensuring young people's preferences are integrated into care planning.(word count = 217)