Since the beginning of the 1980s, historical institutionalism has emerged as one of the most influential theoretical perspectives in social policy studies. Although their work is insightful, most institutionalist scholars tend to relegate policy ideas to the back of their theoretical constructions dealing with welfare state development. The objective of this paper is to show how institutionalist scholarship can pay greater attention to ideational processes without abandoning its core assumptions about the structuring impact of political institutions and policy legacies on welfare state development. If institutions truly influence policy-making, policy ideas matter in and beyond the agenda-setting process. Related to existing policy legacies, perceived problems mesh with policy alternatives grounded in a specific paradigm. When stressing the need to reform, and promoting new alternatives, policy entrepreneurs draw on existing ideological repertoires to frame these alternatives. The ability to successfully frame policy alternatives can become a decisive aspect of the policy process. A discussion of recent European and North American policy debates illustrates these claims.