Regulatory Impact Assessment (RIA) - understood as the formalised analytical activities initiated or carried out by central government administrations when designing specific policy instruments - is currently receiving high levels of political attention. It is seen as a tool to improve regulatory quality and to promote cross-cutting objectives such as sustainable development. Often conceived as an economic analysis of costs and enefits, RIA tends to be depicted as ‘neutral’ assessment process that informs decision makers about ‘facts’. This does not explain, of course, why RIA often becomes an arena for political conflict involving both government departments and stakeholders. Based on empirical research on the design and practical application of RIA across the European Union, this paper explores the relationship between RIA, policy-making and politics. The aim is to shed light on what knowledge is produced, how it is used by different actors and what role it plays in decision-making. Based on this analysis, we explore to what extent and under what conditions RIA can serve as a tool for more evidence-based and sustainability-oriented policy-making processes.