OBJECTIVE: Structural interventions can reduce HIV vulnerability. However, HIV-specific budgeting, based on HIV-specific outcomes alone, could lead to the undervaluation of investments in such interventions and suboptimal resource allocation. We investigate this hypothesis by examining the consequences of alternative financing approaches. METHODS: We compare three approaches for deciding whether to finance a structural intervention to keep adolescent girls in school in Malawi. In the first, HIV and non-HIV budget holders participate in a cross-sectoral cost-benefit analysis and fund the intervention if the benefits outweigh the costs. In the second silo approach, each budget holder considers the cost-effectiveness of the intervention in terms of their own objectives and funds the intervention on the basis of their sector-specific thresholds of what is cost-effective or not. In the third cofinancing approach, budget holders use cost-effectiveness analysis to determine how much they would be willing to contribute towards the intervention, provided that other sectors are willing to pay for the remaining costs. In addition, we explore approaches for determining the HIV share in the cofinancing scenario. RESULTS: We find that efficient structural interventions may be less likely to be prioritized, financed and taken to scale where sectors evaluate their options in isolation. A cofinancing approach minimizes welfare loss and could be incorporated in a sector budgeting perspective. CONCLUSION: Structural interventions may be underimplemented and their cross-sectoral benefits foregone. Cofinancing provides an opportunity for multiple HIV, health and development objectives to be achieved simultaneously, but will require effective cross-sectoral coordination mechanisms for planning, implementation and financing.