Ever growing policy sectors of the EU are managed through a system of composite administration. This does not only apply to regulatory tasks, but also to enforcement powers, and with inspection powers therein. This is the case with some highly relevant policy sectors, such as the European Banking Union, fisheries, food law, competition, financial markets, antifraud provisions and aviation safety. These can either be directly conducted by the EU, where the Commission inspects by itself, or through various forms of cooperation with MS. Focusing on the cases where inspections are conducted in a mixed fashion – that is, where agencies and the ECB are involved together with national authorities – our aim is twofold: first, we try to highlight the different patterns of cooperation emerging between the different administrative levels involved in the inspection tasks; second, we try to investigate what kind of political and judicial accountability mechanisms apply to each model.