AIM: Assesses whether a youth-gambling prevention programme is successful in improving knowledge of gambling activities and develop a more realistic attitude towards those activities. The programme program involves three 60-minute meetings. The objectives of these meetings are to (meeting #1) improve youths' knowledge of gambling activities and help them acquire a more realistic attitude towards these activities; (meeting #2) teach a structured problem-solving approach to resist to peer-pressure; (meeting #3) inform youths of the consequences that may be associated with abusive participation in gambling and teach them to recognize warning signs of a loss of control over gambling habits. METHOD: Uses an experimental design (pre-test, post-test and follow-ups with control group). Overall, 1193 youths participated in this study. Dependent variables: (a) knowledge of and attitudes towards gambling and gambling activities; (b) problem-solving skills; (c) frequency of participation in gambling activities; (d) discussion with relatives, friends and teachers regarding gambling activities and attention paid towards gambling habits among close friends and family. FINDINGS: Participation in the gambling prevention program significantly improves youths' knowledge of the real probabilities of winning and the pitfalls included in gambling activities and favours the development of a more realistic attitude towards these activities. However, the participation in the prevention program does not help to improve problem-solving skills. Nonetheless, it leads more youths to talk about gambling with their parents and teachers, and enables them to be more aware of the gambling habits of their friends and family. It was not possible to verify any decrease in gambling habits as the majority of participants (62%) were non or very occasional gamblers. CONCLUSION: Demonstrates that attitude modification takes place progressively nut that once well assimilated, these new attitudes seem to take hold in a fairly durable way. Acquisition of knowledge seems to take place immediately after the theoretical concepts are taught yet they slightly decreased before stabilising a few months later. The results obtained demonstrate that participation in the prevention program significantly improves youths' attitudes and knowledge regarding gambling activities. The teaching of accurate knowledge and realistic attitudes towards gambling should help youths to recognize the cognitive traps inherent to gambling activities and thus contribute, over the long run, to decrease the number of youths with gambling problems.