At a general level, the article focuses on the relation between states and international organizations. In current era, states and international organizations coexist in international system. Their relation has been researched many times, but the question which is still rather unanswered relates to the management of membership of states in international organizations. The states nowadays participate in hundreds of different organizations. The tricky part that remains to be examined more in details is how to analyse the effectiveness of the engagement of a country in a concrete international organization. The article investigates further the case of the Czech Republic and it analyses its performance and relevance in the European Defence Agency (EDA) applying the research design which was proposed in 20122. The team of researchers proposed four criteria: objective pursued, personal representation, cost/performance ratio and activities implemented. The analysis is based on the examination of the Czech policy goals and priorities in the EDA. It also explor es the area in more details conducting semi-structured interviews with the representatives of different Czech state bodies and employees of the Agency.