For individuals affected by mild psychosocial problems, early psychotherapeutic treatments have the advantage of preventing various pathologies that would otherwise require a medical follow-up. Multiple benefits can thus be obtained for the individual and for the society in general, including present and future treatment cost reductions, as well as the individual's increased potential and productivity once they reach adulthood. A short-term psychotherapy program aimed at pre-school children and adapted to Québec's socio-sanitary context was simulated in order to assess the advantages in terms of quality of life improvements and health service usage reductions. The cost-usage analysis shows that children treated for mild behaviour problems through short-term therapy at a very young age will benefit from a better quality of life. Because they were treated at a very young age or as soon as initial symptoms manifested themselves, these benefits will also increase throughout their life. The costs sustained by the health care system are inferior to traditional treatments and care commonly used for these types of problems.