While research has repeatedly shown the benefits of participation in extracurricular activities for adolescents, few studies have focused on very young children. Extra-curricular activities afford children opportunities for development and can also influence their behaviour. Children's behaviour is an important predictor of their future successes or failures. This study investigated the relationship between behaviour and participation in extra-curricular activities in children aged between five and eight years. Mothers of children (n = 906) in Prep to Year 3 from seven schools in middle- to high-SES areas from a regional city participated in the study. Mothers gave details of their child's extra-curricular activities and used the Strengths and Difficulties Questionnaire (SDQ) (Goodman, 1997) to measure their child's behaviour. Low scores on the SDQ indicate normal behaviour while high scores indicate borderline or abnormal behaviour. Participation, number of activities, and duration of activities were all associated with children's behaviour. Children who participated in extra-curricular activities had lower behaviour scores than those who did not. The results suggest that children benefit from participating in two or more activities for 80-90 minutes per week. (Contains 4 tables.)