This thesis studies the impact of small states in the Common Foreign and Security Policy (CFSP) in EU. The organisation of EU contains an interdependent power relationship between all countries. The aim of this study is to examine how this interdependence affect the influence of small states. Two theoretical framework are used. The first by Robert Keohane och Joseph Nye that developed the theoretical definition of interdependence, while the second one by Søren Christensen and his definition of direct and indirect power. The analytical model contains four hypothesis concerning asymmetrical and vulnerable interdependence, as well as direct- and indirect power. Through a case study of Sweden and Finland the conclusion is that small states have influence in CFSP, but it is limited due to bigger states with much more resources and the geographical position of the countries that creats asymmetrical interdependence. However, Sweden and Finland have influence in the decision-making in CFSP through vulnerable interdependence because of their many international defence cooperations with different organizations that strengthen their national position in the international political system. Also, the formal process of decision-making in CFSP enable direct and indirect power of small states. Therefore, the final conclusion is that small states have influence in CFSP even though is its limited in some aspects.