"The European Commission and other EU institutions take into high consideration inputs from interest groups and lobbies. These organisations provide institutions with technical expertise that policy-makers and bureaucrats from the European Commission, Parliament and Council usually lack. Before drafting a legal proposal, the European Commission regularly announces consultations open to different groups of interests. During these consultations, interest groups, private companies and members of the civil society develop formal and informal networks of coalitions and submit position papers to the European Commission. Coalitions can be different in nature: cross-sectoral, isolated at the periphery of the network, or well-connected. However, within the same consultation, some actors may formally join more than one coalition and present different position papers. Why do coalitions within a policy network take these particular configurations? Why do certain actors decide to join more than one coalition? To answer these questions, this research argues that it is necessary to identify the dynamics that brought actors under the same coalition. The causal mechanisms tested in this research will be the following. First, some actors may join more than one coalition to campaign together with partners they have been traditionally working and lobbying together. Second, structure of coalitions can be shaped by interests shared among the members. Thus, in analysing coalitions that overlap, it is necessary to deconstruct the definition of “interest” and reveal other potential overlapping mechanisms. “Interest” will be divided into three sub-definitions highlighted by the Advocacy Coalition Framework (ACF): core-interests, core-policy preferences and policy instruments. The Advocacy Coalition Framework argues that core-interests and core-policy preferences are the glue that keeps coalitions together. However, this theory neglects to apply these definitions to explain overlapping coalitions. Lastly, the consequences of overlapping coalitions will be disclosed through contributions from the Social Capital and network analysis theories. This research argues that stakeholders placed between two or more coalitions are responsible for the diffusion of policy preferences and instruments. Placed between two or more coalitions, policy brokers develop a communication channel between competing coalitions; which, in turn, can determine the diffusion of ideas. This research will contribute to the Advocacy Coalition Framework (ACF) by arguing that, while core interests still matter in the determination of coalitions and positions, actor-oriented strategies from policy brokers and micro-dynamics at the level of the policy sub-system can play an important role in explaining overlapping coalitions within the same consultation.