This chapter examines the techniques used by health economists to evaluate the value for money of health promotion initiatives. It first provides an overview of concepts related to economics and health economics, including efficiency, equality, equity and accessibility. Efficiency can be evaluated in terms of cost-minimisation, cost-effectiveness, cost-benefit and cost-utility. The chapter then considers the various rationing strategies by which the NHS can try to reduce expenditure, the use of QALYs to compare the cost-effectiveness of health promotion projects, and conjoint analysis. It also explains how health economists calculate the cost to society of unhealthy lifestyles such as obesity and smoking, and goes on to tackle the question of prevention vs cure in health promotion, the expenditure on the NHS, and the limitations of health economics in evaluation of health promotion endeavours. The chapter concludes with an assessment of how to estimate the costs of health promotion.