Mr Durao Barroso says he wants more women commissioners
The new European Commission will have 25 members, one for each EU member state.
The commissioners are appointed for a five-year term, but the entire commission can be dismissed by the European Parliament.
The commissioners are nominated by the member governments in consultation with the incoming president and must win the acceptance of parliament.
However, their job is to act in the general European interest, not to advance the interests of their own country.
When thinking about who to send to Brussels, governments will consider various factors such as EU experience, diplomatic skills and the commission portfolio they may be assigned.
Normal Commissioner: 217,280 euros (£152, 661 / $283,374)
Vice-President: 241,422 euros (£169,622 / $314,859)
President: 266,530 euros (£187,246 / $347,592)
Source: European Commission (Pre-tax figures, from Jan 2004)
Each commissioner has responsibility for a policy area, such as agriculture or competition.
Twenty-four directorates general cover similar policy areas.
The Commission's main job is to initiate new policies. It is sometimes described as the EU's executive arm.
After consultation with member states, interest groups and experts, it proposes legislation to the Council of Ministers and the European Parliament who then decide on it.
The Commission makes sure that EU decisions are properly implemented and supervises the way EU funds are spent.
It also keeps an eye out to see that everyone abides by the European treaties and European law.
The Commissioners are assisted by an administration of about 25,000 civil servants.
These work for directorates-general and specialised departments and are divided mainly between Brussels and Luxembourg.