This panel seeks to build on the literature which has analysed region-EU interactions over the past three decades. All papers focus on the regional dimension of the EU polity, ranging from the characteristics of Brussels-based activities to the domestic effectiveness of EU policies in the regions. To this end, different research perspectives and angles as well as different methodologies – from the more quantitative to the more qualitative – are used. In particular, we revisit and seek to develop controversies in the literature which draw upon perspectives of population ecology, principal-agent relationships, centre-local relationships, federalism, multi-level governance and integration, policy network analysis, tools of comparative politics, and functional territorial interest representation. The first contribution seeks to uncover the institutional determinants of regions both opening and staffing regional antennas in Brussels (Michaël Tatham & Mads Thau). The second maps changes in these antennas’ roles and objectives over time thanks to a repeated-design strategy (Heather Mbaye and Cassie McDonald). The third uses quantitative means to evaluate the determinants of the collective action of regions via their trans-regional networks (Tom Donas & Jan Beyers). Meanwhile the fourth uses qualitative means to study these same networks but focussing on “citizen frames” oriented networking (Justin Greenwood). The fifth draws our attention to the other side of the policy coin namely implementation – as opposed to interest representation – through an analysis of the effective execution of Structural Funds by European regions (Lisa Dellmuth). The panel will be discussed by an expert of comparative and territorial politics, bringing theoretical and conceptual questions into play (Routledge, 2008).