Should we consider local authorities and their associations as a formal government layer when they interact with the European institutions in order to influence EU legislation, or should this be classified as informal territorial interest group behaviour? This paper discusses the role and the influence of local authorities in the European decision-making process. Based on a literature review, the paper contrasts both positions in terms of theoretical underpinning, practical implementation and academic state of affairs. The paper demonstrates that whilst the formal perspective has gained more leeway in the official European policy discourse and subsequent institutionalisation in recent decades, it is often insufficient to guarantee the effective inclusion of local authorities in EU policy-making. Interest group action, i.e. lobbying, might therefore still be a more practical and powerful way of promoting local political interests in the European policy arena.