Introduction. Levels of physical inactivity and sedentary behaviour among English and Spanish youth are high and vary within different regions of each country. Little though is known about these during specific periods of the day. The purpose of this study was to describe PA and sedentary time during segments of the day and week and compare these critical contexts between youth in the Liverpool and Madrid areas of England and Spain, respectively. Methods. PA was objectively assessed in 235 Liverpool and 241 Madrid youth (aged 10-14 years) who wore accelerometers for seven consecutive days. Minutes of sedentary time, moderate PA, vigorous PA, and moderate-to-vigorous PA were calculated for weekdays, weekend days, school time, non-school time, and after-school. Between country differences were analysed using ANCOVAs. Results. Madrid youth spent significantly more time in sedentary activity than Liverpool counterparts. Madrid youth engaged in more minutes of MPA than Liverpool youth during weekdays, school time, and non-school time (P <0.01). Liverpool children recorded more time in VPA than Madrid peers during week days and weekend days (P <0.01), and during school time and after-school periods (P <0.01). MVPA was significantly higher among Madrid youth during non-school time (P <0.01). Around 25% of all youth achieved recommended levels of moderate-to-vigorous PA. Conclusion. Low levels of MVPA and systematic differences in sedentary time, MPA, and VPA exist between Liverpool and Madrid youth. Interventions targeted at the least active children during weekends, after-school, and non-school periods within the cultural contexts common to each city are required.