Public consultations with stakeholders have become a rich and important source of political and policy information that helps bureaucracies to strengthen their informational advantage and enhance their public reputation and legitimacy. Their informational quality depends however on the extent to which they provide useful and usable input. The complexity emerging from the number and diversity of participating stakeholders and issues can easily translate into cacophonous policy input with limited informational value. The structure of the policy space describing the aggregate patterns of stakeholders’ preferences is key to how consultations perform their function as channels of information transmission and venues of preference aggregation. We ask: what is the dimensionality of the policy space of stakeholder consultations and what explains it? We examine forty-two EC consultations organised with the help of online surveys. We find that despite a high variation in the number of stakeholders and issues included in consultations, most events are characterised by a low, two-dimensional policy space. Some consultations also present more than two dimensions. Across most consultations a knowledge dimension coexists with one or more policy substantive dimensions. We find mixed evidence about the effects of consultation design and stakeholders’ participation on the revealed dimensionality of the policy spaces. Our preliminary findings highlight the importance of better understanding the dimensionality of the policy space describing stakeholders’ participation in public policymaking in Europe and beyond. They have important implications for the role performed by public consultations as channels linking citizens, interest groups and bureaucratic decision-makers in public policymaking.