Cost-benefit analysis (CBA) can help policy makers and legislators achieve the greatest social good. Despite the potential role that CBA can play, very little has been done to implement CBA of environmental health interventions (EHIs). The overall aim of this thesis is to improve the quality of CBA analyses of EHIs by addressing important research gaps in the literature. This thesis has four objectives. The first objective is to illustrate a generic framework for CBA of EHIs. The methodological framework described is applied to the economic evaluation of remediating two contaminated industrial sites in Sicily (Gela and Priolo). Including children’s health benefits in CBA is challenging. Compared to adults, children are more vulnerable to environmental hazards, however, due to the lack of child specific willingness to pay (WTP) measures children’s health benefits are often excluded from the analysis or valued using adults WTP measures or cost-of illness estimates. The second objective of the thesis is to investigate children’s ability to understand WTP questions. In particular, the thesis investigates if children are able to understand health risk and money-related concepts. The third objective of the thesis is to evaluate child (aged 7-18 years) and parental WTP for reducing children’s environmental health-related risk of asthma attack using both a contingent valuation study (CV) and a discrete choice experiment (DCE). The fourth objective of the thesis is to estimate the potential benefits to pupils of reducing traffic-related air pollution near primary schools in London using the WTP values quantified in the CV study and environmental and health data collected in London primary schools. The results of this thesis show that that, despite the high remediation cost, the clean-up of Gela and Priolo in Sicily can be highly cost-effective. The findings of the studies investigating whether children are able to understand WTP questions show that even younger children are able to understand health risk information and money related concepts and that their ability to do so improves with age. Both the CV and the DCE study show that children are able to provide rational answers to WTP questions. Results of the contingent valuation study also show that parents’ WTP estimates differ significantly from those of their children. Including children’s health benefits and preferences, as demonstrated in the practical case of improving air quality in proximity of London primary schools, gives more accurate and precise estimates of the real benefits arising from EHIs. It also provides a transparent and reliable source of information for decision makers. Findings from this thesis can improve the quality of CBA of EHIs and help future studies provide a sounder basis for policy making.