The aim of the current study was to examine and compare dieting and unhealthy weight-control behaviours (UWCB) in population-based samples in two large urban areas in Spain (Barcelona) and in the USA (Twin Cities of Minneapolis and St. Paul, Minnesota). Additionally, use of UWCB across weight categories was explored in both samples. Participants included 1501 adolescents from Barcelona (48% girls, 52% boys) and 2793 adolescents from the Twin Cities (53% girls, 47% boys). The main outcome measures were dieting, UWCB (less extreme and extreme) and weight status. Although dieting and UWCB were prevalent in both samples, particularly among girls, the prevalence was higher in the US sample. In both countries, the report of dieting and use of UWCB was highest among overweight and obese youth. Prevention interventions that address the broad spectrum of eating and weight-related problems should be warranted in light of the high prevalence and co-occurrence of overweight and unhealthy weight-related behaviours. Copyright © 2012 John Wiley & Sons, Ltd and Eating Disorders Association.