UEFA are to scrap the second round of the Champions League from the 2003-2004 season onwards.
There will still be 32 clubs involved at the start of the competition proper once the qualifying rounds have been completed.
Eight groups of four will compete in group stage one. There will then be a two-leg knockout system for the last 16, the quarter finals and the semi finals.
UEFA president Lennart Johansson, who chaired the meeting, said the format changes had been made with the best interests of the competition and European football in mind.
"We believe this reduction in the size of the competition is in the longer-term interests of everyone involved - clubs, players, fans, broadcasters, sponsors and European football in general," he said.
"It is not easy to change a competition which is recognised as the best club event in the world, but sometimes you need to act for the future.
"We have been listening carefully to our stakeholders, and it is clear that there are a variety of views - however, we believe this is a moment for leadership in the wider interests of the game.
"As the European governing body, UEFA has to consider many different factors, both sporting and commercial, and at the same time think ahead.
"We want to see a better balance in European football, a less congested fixture list for players and clubs and a flagship competition which has the right sporting mix and brand strength.
"We believe that this move will send the right signals to the whole of European football about how we can work together to tackle some of the challenges ahead."
PA