Representations of sub-national entities challenge since the mid-1980s the monopoly of the central states on EU representation. Through an analysis of their activities, this article verifies whether their presence may be interpreted as an expression of the hollowing out of the state. The research revealed that these representations have developed a national and an international strategy to fulfil their mission. The international strategy resembles that of interest groups in the European policy space, and it follows the neo-functionalist logic of other European interest groups. The national strategy is more policy-oriented. To influence the decision-making process, representations form networks between themselves and with their permanent representation. Rather than hollowing out the state, the activities of these representations reveal a growing interdependence between the central state and regional authorities resulting from European integration.