A meta-analysis of North American studies indicates that the prevalence rate of pathological gambling varies between 4.4% and 7.4% among adolescents. Pathological gambling is thus not a phenomenon that suddenly appears once youths reach an adult age. On the contrary, significant contact with gambling occurs in childhood adolescence. For this reason, it is important to develop an effective gambling prevention program that will reduce the risk that youths will develop gambling problems. The information promoted in the prevention program our research team created and evaluated here teaches youths to recognize the traps of gambling activities, while enabling them to make an informed decision as to their eventual participation in those activities. The program is based on knowledge and recognition of key indices that can be easily identified as warning signs of a loss of control. It is predicted that youths who participate in this prevention program will improve their knowledge of gambling activities and will develop a more realistic attitude towards those activities than youths from a control group. The experimental group's problem-solving skills are also expected to improve. An experimental design (pre-test, post-test and follow-ups with control group) was used to evaluate the program's effectiveness. Overall, 1193 youths participated in this study. The prevention program involves three 60-minute meetings. The objectives of these meetings are the following: (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. (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. 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 their 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. Finally, note that it was impossible to verify any decrease in gambling habits as the majority of participants (62%) were non or very occasional gamblers. However, no iatrogenic effect was observed on the frequency of participation in gambling activities. Aside the positive impact of the program on the attitudes and knowledge of students, participation in the preventive sessions contributed to create a dialogue with adults and increased youths' interest in the gambling habits of their friends and family. These discussions enabled the youths to validate the information they received during class, to consolidate what they learned during the prevention sessions, and favour the dissemination of this knowledge beyond the scope of the academic environment. The results obtained regarding youths' attitudes and knowledge demonstrate that attitude modification takes place progressively. However, once well assimilated, these new attitudes seem to take hold in a fairly durable way. On the other hand, acquisition of knowledge seems to take place immediately after the theoretical concepts are taught. Yet, they slightly decreased before stabilising a few months later. This suggests that assimilation of new knowledge may be optimized by the addition of an intervention session a couple of months after the end of the intervention. Even if it was impossible to verify any decrease in participants' gambling habits, it is possible to think that the impact of participation in the gambling prevention program could be observable and measurable within a few years. However, only a long-term follow-up study would make it possible to assess whether participation in the program does indeed contribute to decreasing gambling habits and the number of youths who regularly participate in gambling activities. Despite the non-significant results observed for problem-solving skills, it seems nonetheless important to include this component, which benefits from great theoretical support, especially within the framework of prevention programs targeting youths. However, the teaching method must be changed in order to maximize the intervention's effectiveness. Despite some methodological limitations observed during the evaluation of this program, the results obtained clearly 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.