Economic evaluations of interventions for children and adolescents with mental health problems are comparatively rare, although the growing need for them is now quite widely recognized. This review paper first explains how demands for such evaluations have built up, and for what reasons, and then considers the response from evaluators. The various modes of economic evaluation are introduced and illustrated. Previous and current research is discussed by reference to five generic research questions commonly addressed in the wider health economics field: What treatment should be provided? When? Where? To whom? How? The review concludes with recommendations as to how economic evaluations should be taken forward in this increasingly important area of intervention.