The subject of this thesis is the Imperial Presidency. Arthur Schlesinger is the author of this term in the realm of Political Science. His book was a reaction to the gradual accretion of political power in the office of the President of the United States. Imperial Presidency is described by variables: a) The President overreaches his powers given to him by the Constitution of the USA; b) The President is not limited by other branches of power. The theories behind this thesis are called the unilateral action theory and the unitary presidency theory. After designating variables in the thesis we should be able to answer the question: "What kind of political behaviour describes imperial presidency?"