After the eastern enlargement of the European Union in May 2004 it became clear that the Union can not continue to function under the existing treaties and had to be reformed. The Treaty of Nice that came to force in February 2003 was supposed to reorganize the institutional structure of the EU but the reform was not sufficient. When the Treaty establishing a Constitution for Europe (TeCE) was signed in October 2004 it was not very well accepted by some of the Member States and became a subject of criticism mainly for its constitutional character. Objections were raised that this Treaty would transform the EU into some kind of a superstate, which originated a discussion among the political discourse about the sovereignty of the Member States; the Treaty was then rejected in Netherlands and France. At the end of December 2007, after many months of comprehensive bargaining and discussions the Lisbon Treaty (the Treaty on the Functioning of the European Union), was signed in Portugal during the German presidency. This document is basically modified version of TeCE where the criticized points were either removed or adjusted to its objections. The Treaty came into force in 1 December 2009 following the ratification process in all the 27 Member States. This paper aims to provide a clear account on the changes that comes along with the Lisbon Treaty being in force. Even though the modifications do not have so far-reaching consequences as was previously planned within its unsuccessful predecessor, the European Constitution, the impacts are still substantive and deserve our attention and comprehensible demonstration. Hence the first part of the paper is dedicated to the account of the modifications brought in by the ratification of the Lisbon Treaty, mainly on how are these changes going to modify the institutional settings and some policies. A short report is given on the process of ratification of the Treaty in the EU Member States to summarize the historical implication
