The first official name for the Lisbon Treaty was the "Reform Treaty" which was formally changed by the signature in Lisbon.

The EU Constitution was first adopted by the Heads of State and Government on 18 June 2004. It was then solemnly signed in Rome on 29 October 2004. However, on 29 May and 1 June 2005 it was rejected by referendums in France and the Netherlands after which a "period of reflection" was launched, together with the Commission's "Plan D - for Democracy, dialogue and debate." During this time some other states ratified the rejected constitution.

The Berlin Declaration (25 March 2007) restarted the so-called “constitutional process”. The then new German chancellor Angela Merkel succeeded - through secret diplomacy - to reach agreement on restarting the constitutional process. On the 21-23 June 2007 Summit, Merkel concluded the German EU presidency with the adoption of a very detailed negotiation mandate for a new intergovernmental conference.

The intergovernmental conference started one month later, on 23 July 2007. The new Portuguese presidency aimed at finalising the negotiations for a special summit in Lisbon, on 18 -19 October 2007, allowing for the revised constitution to be signed before 2008 so as to enter into force before the European elections in June 2009.

The Lisbon Treaty includes all operational articles from the rejected EU Constitution, but it alters the presentation radically. Instead of one comprehensive document, the Lisbon Treaty further amends the existing 17 basic EU treaties and many more protocols and declarations.

The EU's constitutional law will thus continue to consist of a plethora of treaties amending the founding treaties. The Lisbon Treaty includes more than 3000 pages compared to the 560 pages in the rejected constitution. Although it changes the name from “Constitution” to “Lisbon Treaty”, iit does not alter the jurisdiction of the European Court which characterises the treaties as ”the Constitutional Charter of a Community of Law, a new legal order for the sake of which the States have limited their sovereign rights” (Opinion 1/91).

The Lisbon Treaty deletes the article on the European symbols, such as the flag, the Europe day, the currency, the motto and the common anthem. However, it is also stated that this deletion does not change any of the status of the European symbols.

The Lisbon Treaty moves article I-6 of the Constitution referring to the primacy of Community law into Declaration no 17. It nonetheless recalls the existing case law of the European Court, which states e.g. that EU law cannot “be overridden by domestic legal provisions, however framed” (Case 06/64 "Costa/ENEL").

The Lisbon Treaty contains the same number of areas subject to votes by qualified majority and even adds two new fields where qualified majority voting (QMV) can be used: Energy solidarity and Climate change. The revised constitution now contains 68 new articles with majority voting.

The revised constitution abolishes the existing pillar structure and gives legal personality to the Union making it possible for the entire Union to act on the international scene in Art. 47.

It also establishes a common permanent president for the European Council and a foreign minister who will now be titled “High Representative of the Union for Foreign Affairs and Security Policy”. This High Representative – currently a post held by Javier Solana- will also be the vice President of the European Commission.

The term European Community disappears in all treaty texts and is replaced by the term “Union”.

The Charter of fundament rights is made legally binding allowing the EU Court to further develop the legal principles and fundamental rights of the Union. See Art. 6 TEU.