Policy-makers often wish for clear advice on the basis of absolute certitude about the consequences of new policy measures. Yet, such certainty is not feasible in an uncertain world. Nevertheless, decision makers do not have to do without recommendations that are derived from sound scientific analysis. The tools of evidence-based policy advice provide credible assessments on the likely outcomes of political decisions. What exactly is meant by “evidence-based” policy advice? Institutes such as the RWI reach their findings through transparent combinations of theory-based assumptions and empirical data. On this basis, they derive clear policy recommendations but also document the restrictions of their analyses. The present RWI Position policy paper highlights opportunities and restrictions of evidence-based policy advice by examples from different fields of research at RWI. Thus, this paper illustrates the institute’s new claim “Research with Impact”. The addition “with impact” is to be understood in a threefold sense: first, virtually all projects at RWI are of practical relevance and possess a high degree of potential policy impact. Second, research at RWI fulfills highest academic standards and research results are regularly published in renowned academic journals (i.e. with a high “impact factor”). Finally, the empirical establishment of cause-effect relationships, also called “impact evaluation”, is a trans-divisional core competency of RWI and, therefore, often the central challenge in research and policy consulting projects at the institute.