Purpose: The purpose of this paper is to gain insight into the extent to which Dutch children are aware of their own physical activity level, and to what extent children's physical activity is habitual. Special attention was paid to the potential moderating effect of "awareness" and "habit strength" on the association between psychosocial factors and exercise behaviour. Design/methodology/approach: Data were gathered on 419 Dutch children, aged eight to 13 years, with self-administered questionnaires in which demographic variables, reported physical activity levels, psychosocial factors and levels of awareness and habit strength were assessed. Findings: Children with high awareness of personal behaviour and high habit strength were reported to be more physically active. Furthermore, psychosocial factors were less associated with physical activity in children with low awareness of their personal physical activity levels and in children for whom physical activity was strongly habitual than in children with high awareness or with low habit strength concerning physical activity. Research limitations/implications: The paper uses self-reports to measure physical activity, which gives less accurate information on physical activity behaviour than objective measures. Furthermore, the cross-sectional nature of this study design precludes the authors from inferring causal relationships between psychosocial factors and physical activity behaviour. Practical implications: For promoting physical activity in children to be successful, it is important that education is first aimed at raising awareness levels. Besides, strengthening the habitual nature of physical activity in children might help to establish higher levels of physical activity. Originality/value: The study indicates the importance of the concepts "awareness" and "habit strength" in physical activity behaviour. It offers useful information for designers of interventions to improve physical activity in children. (Contains 1 figure and 2 tables.)