Little research has been done to connect health promotion programs to outcomes in terms of life expectancy, health care costs and cost-effectiveness. For a policy maker, economic evaluation may be an important tool to support decisions on how to allocate the health care budget. The aim of this paper was to determine the cost-effectiveness of a Dutch school-based smoking education program. The incremental cost-effectiveness ratio of the school program was estimated at €19 900 per quality adjusted life year gained. For a complete analysis, not only intervention costs but also savings for smoking-related diseases and differences in total health care costs should be taken into account. As several assumptions had to be made in order to estimate cost-effectiveness, the study outcomes should be interpreted with caution. Main problem in estimating the cost-effectiveness was the lack of proper effectiveness data on daily smokers among adolescents. Absence of specific effectiveness data often is an obstacle in the economic evaluation of public health interventions. While some problems may be the result of insufficient sample size or follow-up, another possible explanation might be the different basic principles of analysis of health promoters and economists.