The purpose of this thesis is to examine whether the individual political leader is important for the analysis of international relations. Traditionally the focus of investigation in international relations has been on the nation-state, or the systems level, and as a result the individual level has been somewhat neglected. Using the theory of political psychology there is a possibility of finding nuances that might not be found if the focus of the investigation is on the nation-state. With the help of key concepts such as personality, emotion, cognition, and social identity decision making that has affected world politics have been examined. An empirical examination of the political psychology has been made by applying the theory to a case study, George W Bush. By applying the theory of political psychology to the decision making process used by George W Bush and his Administration it will be shown that the individual can impact world politics, especially in the case of the invasion of Iraq. Furthermore, one of the flaws of the theory of political psychology, its problem in handling the concept of global terrorism, is briefly discussed. The conclusion that has been drawn in this thesis is that the individual level of analysis is just as important as the systems level or the domestic level of analysis.