This article reviews a central strand of the literature on legislative decision-making in the European Union (EU): procedural spatial models. These models have gained increasing prominence during the last decade of scholarship on the EU and have considerably enhanced our understanding of the EU legislative decision-making process. However, the literature has not been without criticism and has reached a stage of theoretical stagnation. The intention of this article is therefore twofold: First, it reviews the existing procedural spatial literature and critically discusses the lacking specification and justification of some of its assumptions. The manifold assumptions used in different models are based on actors' preferences and the characteristics of the decision-making process, which are often at odds if not diametrically opposed to each other. In a second step, it will therefore be argued that it is necessary to re-evaluate some of the central assumptions of procedural models. In particular, future research needs to study mechanisms of preference formation and decision-making, i.e. aggregation of preferences, within EU legislative bodies.