In 2005, the Australian Child and Adolescent Obesity Research Network (ACAORN) addressed the question, "What childhood and adolescent obesity research questions remain to be addressed through longitudinal research?" Using the Delphi Technique, ACAORN members individually generated then refined and prioritised a set of research ideas. When delegates to a national child obesity symposium repeated the final (prioritisation) step, a strong concordance in rankings was evident. The highest-priority questions related to modifiable environmental risk/protective factors; parental and family factors; longitudinal relationships between development of obesity and physical, social and mental health; predisposing prenatal and early childhood patterns of growth and nutrition; identification of stronger early markers of later chronic disease risk; and better understanding of the natural course of overweight in childhood. These prioritised research questions could be proactively provided to funding bodies, quoted to support research applications, and used to stimulate secondary data analysis and collaborations between research groups.