OBJECTIVE: To investigate whether adolescents living in a high-walkable town centre are more physically active than those living in a less-walkable suburb. METHODS: This cross-sectional study was conducted in Izegem (Belgium). Data collection took place in spring 2007. One high-walkable urban neighbourhood and one less-walkable suburban neighbourhood were selected, based on objective connectivity and residential density. One hundred twenty adolescents (12-18 years, 60 per neighbourhood) completed the Neighbourhood Environmental Walkability Scale (NEWS), the Neighbourhood Physical Activity Questionnaire (NPAQ), wore a pedometer for 7 days and filled in an activity log. RESULTS: In contrast with the expectations, adolescents living in the less-walkable suburb reported 220 min/week more cycling for transport than those living in the high-walkable town centre. A trend towards significance was found for mean step counts/day with 1371 more steps/day for suburban adolescents. Travel time to school was 7.4 minutes less for urban adolescents. CONCLUSIONS: In contrast with previous results in adults, lower walkability and larger distance to school was associated with more physical activity in Belgian adolescents. Therefore, physical environmental interventions designed for adults, focusing on increases in connectivity, residential density and connectivity, might not be effective for Belgian adolescents.