This paper examines the creation of independent agencies within the EU, such as the European Environment Agency (EEA) and the European Central Bank (ECB). Majone and others have argued the case for European regulatory agencies. Such agencies can provide for continuity, expertise, accountability and effective authority – in short, an institutionalisation of responsibility. Against this optimism, I argue that a dilemma of institutional design naturally arises from the agencies’ situation in the EU. On the one side, we risk creating powerful agencies that institutionalise monomania– that is, agencies that single-mindedly and all-too-effectively pursue narrow agendas, inadequately checked by other bodies. On the other, we are also likely to encounter relatively impotent agencies which institutionalise schizophrenia– that is, agencies that must scout around for audience and support, and hence are unable to act effectively.