Policy reforms to children's services in the UK and elsewhere encourage a greater focus on outcomes defined in terms of child well-being. Yet for this to happen, we need not only a better understanding of what child well-being is and how services can improve it, but also the ability to measure child well-being in order to evaluate success. This book investigates the main approaches to conceptualising child well-being, applies them to the child population using household survey and agency audit data, then considers the implications for children's services.