Analyses of the significance of knowledge in present-day society, also referred to as knowledge society, fuelled our curiosity about the role that experts play in international and European decision-making processes. This interest prompted us to ask the question reflected in the title of this book: are experts in these decision-making processes advisors, decision makers or irrelevant actors? A literature survey illustrated that, while analysis of knowledge utilization is and has been ’ readily available in the social sciences, there is only scant analysis of how experts relate to decision-making processes at the international and European levels. This realization in turn prompted us to bring together a group of, yes, ’experts’ to discuss the above-mentioned question at a two-day seminar held in June 2011, which is at the origin of this book.