Economic models to inform decision-making are gaining popularity, especially for preventive interventions. However, there are few estimates of the long-term returns to parenting interventions used to prevent mental health problems in children. Using data from a randomised controlled trial evaluating five indicated parenting interventions for parents of children aged 5-12, we modeled the economic returns resulting from reduced costs in the health care and education sector, and increased long-term productivity in a Swedish setting. Analyses done on the original trial population, and on various sized local community populations indicated positive benefit-cost ratios. Even smaller local authorities would financially break-even, thus interventions were of good value-for-money. Benefit-cost analyses of such interventions may improve the basis for resource allocation within local decision-making.