This doctoral dissertation covers the topic of economic aspects of health promotion and primary prevention. As this is a very broad research field, it focuses on the example of physical activity and in parts also on the target group of children and adolescents. It consists of seven chapters. Chapter 1 gives general reasons for economic evaluation of primary prevention and health promotion programs, especially in the field of physical activity and for the target group of children and adolescents. Furthermore, the research questions of this thesis are specified and an overview of what this doctoral dissertation adds to research knowledge is given. Chapter 2 presents the results of expert interviews on the most important aspects of the implementation of (economic) evaluations in health promotion and primary prevention programs (for children and adolescents). Chapters 3 and 4 deal with the existing literature on economic evaluations of programs encouraging physical activity in children and adolescents. They analyze the same underlying literature from different perspectives. Chapter 3 focuses on the transferability of the results of the program to other contexts. In contrast to that, chapter 4 examines the quality of existing economic evaluations on this research topic. It became apparent from these two chapters that there is not much evidence on the economics of programs encouraging physical activity in children and adolescents. This is mainly due to missing cost data. Therefore, chapter 5 provides a method of documenting the resource use and the resulting costs of those programs by offering a cost module including a description of how to use it. In chapter 6, a cost study of an existing and effective primary prevention program (JuvenTUM) is conducted and the results are presented. Finally, in chapter 7, the principal findings of the thesis are summarized, its limitations discussed, and future research as well as implications for health policy and management are addressed.