BACKGROUND: Physical inactivity levels are increasingly prevalent among Ecuadorian adolescents. School-based interventions can be potentially effective in promoting physical activity but must be informed by cultural-specific factors. METHODS: Twelve focus groups were carried out with adolescents (N=80) in rural and urban Ecuador to identify factors influencing physical activity. Additionally, four focus group discussions with parents (N=32) and four with school staff (N=32) were conducted. Individual and environmental factors were questioned using the 'Attitude, Social influences and Self-efficacy' model and the socio-ecological model as theoretical frameworks. RESULTS: Factors influencing physical activity varied between groups. In the rural area farming and norms for girls impeded leisure-time physical activity, whereas urban groups emphasised traffic and crime concerns. Groups from a low socio-economic status more frequently mentioned a fear of injuries and financial constraints. Several factors were common for all groups including preferences for sedentary activities, poor knowledge, time constraints and laziness, as well as a lack of opportunities at home and school, unsupportive parental rules and lack of role models. CONCLUSION: A conceptual framework including the identified factors emerged to inform the design of a cultural-sensitive school-based intervention to improve physical activity among Ecuadorian adolescents. Future interventions should be tailored to each setting.