Adolescent obesity and physical inactivity are serious health issues in Australia.Using a Theory of Planned Behaviour framework (Ajzen, 1991), the present study aimed to investigate if belief-based differences exist between those adolescents who perform moderate-to-vigorous physical activity on a regular basis (performers) and those who do not (non-performers).Participants, comprising of 395 grade nine students, completed a questionnaire assessing their physical activity beliefs and reported their physical activity 1 week later.The results revealed that the attitudinal, normative, and control beliefs of performers and non-performers differed significantly.The findings provide important applied information that can be utilised in developing intervention programs aimed at increasing adolescent physical activity.