A breakdown of the key elements in treaty.
A full-time president of the European Council elected for 2½-year terms.
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 the existing 27 from 2014.
A move to "double majority" voting in 2014 (with a three-year phase-in period).
A reduction in national vetoes in about 40 different policy areas, mainly in justice.
Extension of European Parliament and European court scrutiny to these policy areas.
Britain and Ireland can opt out or opt in to sensitive justice proposals by commission.
National vetoes remain in foreign affairs, defence, tax, defence, social security and culture.
National parliaments get more time and powers to scrutinise EU proposals.
If ratified, the "reform treaty" will lift a block on future enlargement of the EU.
Candidate states must promote EU values to join bloc.
At the insistence of Lithuania and Poland, there is a reference to energy solidarity.
An article enabling member states to withdraw from the EU is also included.
The EU gets a single legal personality and can now sign international treaties.
Enhanced co-operation can now start with nine states rather than one-third of states.
The treaty refers to a particular need to combat climate change.