This chapter reports on an on-going effort in Sweden to create a societal benefit-cost model for evaluation of causal effects of interventions for supporting children and young people at some developmental risk. This work is motivated by needs for such evaluation tools in planning, selection and follow-up of public and private impact investments. So far, modules have been created for economic evaluation of life-course, labour-market-related outcomes, some short- and medium-term cost offsets and the value of mortality and morbidity effects. On-going work includes estimation of the willingness to pay for suicide prevention and the costs of crime. However, as indicated by two case studies that are briefly summarised, even incomplete estimates of the benefit side are sometime sufficient to indicate high societal returns of early intervention and prevention measures.