OBJECTIVES The Health-promotion through Obesity Prevention across Europe (HOPE) project aims to bring the European scientific knowledge on overweight, obesity and their determinants together and use the expertise of researchers across Europe to contribute to tackling the obesity epidemic. DESIGN/SUBJECTS/RESULTS This special issue of Public Health Nutrition presents important results from one of the work packages of the HOPE project that aims at gaining and integrating knowledge on the determinants of nutrition, physical activity and obesity among schoolchildren and adolescents (aged 10-18 years) in different European regions. It includes contributions from Northern Europe (Norway), Central and Eastern Europe (Germany, Poland and the Czech Republic), Southern Europe (Greece) and Western Europe (Belgium and The Netherlands), as well as an overview of the availability of good-quality data on prevalence rates and trends in overweight (including obesity) among adolescents in European Union (EU) countries. The studies that are included report prevalence differences, data on relevant nutrition and physical activity behaviours, as well as potential physical and environmental behavioural determinants. CONCLUSION These papers provide further evidence on differences in obesity and overweight prevalence among different EU regions and countries, and contribute to the further exploration of risk factors that may or should be addressed in obesity prevention efforts for school-aged children and adolescents in EU countries.