There is a growing interest among health promotion researchers to better understand and influence the policy process. However, at this point in time, theoretical concepts enabling researchers to do so are still rare and underused, suggesting a need for new, easy-to-use concepts to explain successes or failures of health promotion policies. This article presents the ADEPT (Analysis of Determinants of Policy Impact) approach, which aims to explain and influence policy development and policy impact implementation with four determinants: goals, obligations, resources and opportunities. ADEPT provides a detailed operationalization for both quantitative and qualitative use. An empirical test of the ADEPT model using a quantitative survey of 719 policy-makers from four health promotion policy fields and six European nations indicated that both policy outputs and policy outcomes are influenced by the four determinants. The approach has, in the meantime, been successfully utilized to analyze and initiate policy development in a number of health promotion projects. Despite a number of limitations, ADEPT provides an easy-to-use, theory-based and parsimonious tool for understanding and influencing policy processes in health promotion. Moreover, as it identifies potential 'levers of influence' and can easily be connected to existing methods of community development or capacity building, it is a particularly powerful tool for policy development.