The Lisbon Treaty, known until now as the reform treaty, was drafted as an alternative to the constitutional treaty that had been defeated in referendums in France and Holland.
Unlike the latter, a straightforward, easy-to-read replacement for all previous treaties, the Lisbon Treaty, although touted as "simplified", is a hugely complicated collection of amendments to previous documents.
It is also shorn of such constitutional trappings as a flag or anthem for the EU.
And, while the Charter of Fundamental Rights and clauses giving the union a legal personality were part of the constitution, they have now been relegated to protocols, though they retain legal force.
Main points of new treaty:
A full-time president of the European Council elected for 2½- year terms, renewable once.
A new High Representative of the European Union for Foreign Affairs and Security Policy, who sits on the commission and chairs EU foreign ministers' meetings.
The number of commissioners falls to 18 from 27 in 2014. Each member state gets the right to appoint a commissioner in rotation.
A move to double-majority voting in 2014 with a three-year phase-in period.
National vetoes are dropped in almost 50 policy areas, including the sensitive justice field.
The European Parliament and the European Court of Justice get proper scrutiny powers in the new areas that move to qualified majority voting.
Ireland and Britain have negotiated opt-outs and opt-ins in the sensitive justice field.
National vetoes remain in the field of defence, foreign affairs, tax, social security and culture.
Parliament will have 751 members in 2009. Ireland gets 12 MEPs, one fewer than now.
A procedure has been established to enable member states to choose to leave the EU.
The union gets a legal personality, meaning it can negotiate international agreements.
National parliaments get more time and powers to scrutinise commission proposals
The treaty refers to a particular need to combat climate change and makes reference to the need for solidarity when it comes to negotiating with energy suppliers.
Portugal, the current holder of the EU presidency, has stipulated that the Lisbon Treaty should be ratified as early as possible during 2008 so as it can come into force in January 2009. Germany, France and Poland are all vying to be the first states to ratify it, possibly as early as February.