This thesis deals with the Czech Presidency of the Council of the European Union in the first half of 2009 in terms of energy and energy security. In the introductory theoretical part the notion of "energy security" is defined and the chapter analyzes energy in the EU primary law too, including jurisdiction of the issue to a particular Union's institutions. In the practical part of the thesis the priorities of the EU in energy and energy security are described and steps that CZ PRES made to increase EU energy security are analyzed. Particular emphasis is placed on the gas crisis and the general supply of gas, which played during the Czech Presidency a significant role. Final chapters focus on the shift in the EU's energy security during the...