By Jonathan Marcus
BBC diplomatic correspondent
The restrictions hampering the use of Nato forces in Afghanistan were the most contentious issue at this summit.
The leaders have gone at least some way to resolving the problem.
The Alliance's Secretary General, Jaap de Hoop Scheffer, said that some 20,000 of Nato's 32,000 troops deployed in the country would now be able to be used with greater flexibility.
Nato operations in Afghanistan should benefit from a troop boost
These restrictions have been a serious bone of contention in Nato, highlighting that a small number of countries, like Britain and Canada, have been shouldering the brunt of the fighting in southern Afghanistan and, inevitably, suffering the bulk of the casualties.
British Prime Minister Tony Blair, who has been very much in the lead in terms of emphasising that Afghanistan represents Nato's new front-line, emerged from this summit relieved that some progress had been made.
Pledges and promises
More than just the removal of some caveats and the pledges of additional troops, he stressed that everyone around the table now accepted the critical importance of the mission in Afghanistan for Nato's future.
Additional troops and training teams have been offered by several countries and France has agreed to send more helicopters and aircraft.
The Nato Secretary General said that Alliance commanders now have 90% of what they needed in Afghanistan - so, he accepted, there was still some more work to be done.
Indeed, the impact of the pledges made here in Riga is uncertain.
The test will come in combat in Afghanistan over the coming weeks and months.
The summit also discussed Nato's partnership activities issuing an invitation to three Balkan countries - Bosnia-Herzegovina, Montenegro and Serbia to join the Partnership for Peace programme.
Nonetheless, the summit communique stressed again Nato's concerns that Serbia and Bosnia-Herzegovina must co-operate with the International Criminal Tribunal for the former Yugoslavia and bring alleged war criminals to justice.
Deep divisions remain between Nato member states
The communique said that Nato would closely watch their respective efforts in this regard - a clear sign that ever closer ties with Nato - perhaps ultimately even membership - will depend upon their compliance here.
There will also be stepped-up training with countries around the Mediterranean and in the Middle East.
Language relating to closer ties with countries like Japan and Australia - way beyond the Alliance's traditional area of interest - was less explicit than some had wanted; a reflection of the divisions within Nato about the Alliance's long-term future.
Success or failure in Afghanistan will have a powerful influence over the direction that the Alliance goes.
Is Afghanistan to be a one-off operation? Or is it simply the shape of things to come, heralding a more globalised Alliance for 21st Century?
Nato has some fundamental questions to answer, but Riga was not the time or the place to provide such answers.
No aspiring countries were invited to join the Alliance at this summit. But the Secretary General said that Nato's door remained open and that every effort would be made to assist aspiring members over the threshold.
All in all then a business-like meeting that did not, perhaps, live up to its billing as a "transformational" event.
Nonetheless, the fact that it was held here in Latvia - not so long ago territory that was part of the former Soviet Union, shows how the political history of Europe has changed over little more than a decade.
Nato too has changed a lot. But its supporters and its critics at least agree on one thing: it still has a long way to go to recreate the sense of purpose and common destiny that it had during the Cold War.
MAIN FLASHPOINTS IN AFGHANISTAN
There are 32,500 Nato-led troops in Afghanistan
Main troop contributors: US, (11,800), UK (6,000), Germany (2,700) Canada, (2,500) Netherlands (2,000), Italy, (1,800) and France (975)