BACKGROUND: Physical activity provides fundamental health benefits and plays a positive role in physical well-being. The aim of this present study was to investigate whether a 6-month physical activity program could influence physical self-esteem and frequency of physical activity in physically inactive female high school students in short- and long-term periods and whether personality traits were related to physical activity behaviour and compliance with the program. METHODS: The study was a cluster-randomised controlled intervention study including 104 physically inactive female high school students aged 16-19 years, 60 females in an intervention group and 44 females in a control group. The intervention group exercised at sport centres at least once per week during a 6-month period. Questionnaires were used for evaluation. RESULTS: At a 6-month follow up, the intervention group improved physical self-perception in all subdomains and significantly improved physical condition, physical self-worth and self-related health compared to the control group. At 1-year follow up, 25 females out of 53 females were still physically active, and all ratings remained almost the same as at the 6-month follow up. There were no particular personality traits that were dominant in the groups. CONCLUSION: A 6-month physical activity program can positively influence physical self-esteem and the frequency of physical activity, both from a short- and long-term perspective.