Cost-effectiveness analyses of health care programmes often focus on maximising health and ignore non-health impacts. Assessing the cost-effectiveness of public health interventions from a narrow health care perspective would likely underestimate their full impact, and potentially lead to inefficient decisions about funding. The aim of this study is to provide a practical application of a recently proposed framework for the economic evaluation of public health interventions, evaluating an intervention to reduce alcohol misuse in criminal offenders. This cross-sectoral analysis distinguishes benefits and opportunity costs for different sectors, makes explicit the value judgements required to consider alternative perspectives, and can inform heterogeneous decision makers with different objectives in a transparent manner. Three interventions of increasing intensity are compared: client information leaflet; brief advice; brief lifestyle counselling. Health outcomes are measured in quality-adjusted life-years and criminal justice outcomes in re-convictions. Costs considered include intervention costs, costs to the NHS and costs to the criminal justice system. The results are presented for four different perspectives: ‘narrow’ health care perspective; criminal justice system perspective; ‘full’ health care perspective; and joint ‘full’ health and criminal justice perspective. Conclusions and recommendations differ according to the normative judgement on the appropriate perspective for the evaluation.