The marchers, hoisting Lebanese flags with black ribbons and anti-Syrian placards and chanting "Syria out", demanded the implementation of a UN Security Council resolution calling for an end to Syrian intervention in Lebanese affairs.
Riot police were deployed on Friday along the route of the demonstration in the Lebanese capital and around the offices of Syrian-backed Prime Minister Umar Karami in the city centre.
The unauthorised march was called by several opposition groups, including exiled anti-Syria Christian leader General Michel Aoun, to mark Lebanon's independence day on Monday.
Similar protests in the past ended in clashes between demonstrators and police, but Friday's march was proceeding peacefully after the authorities said they would tolerate the procession if it was held in an orderly manner.
"Towards true independence and an end to Syria's hegemony over Lebanon," a placard raised by demonstrators said.
"There is no independence with the presence of Syria in Lebanon," Hadi Kusan, a 26-year-old demonstrator, said.
After several pullouts, Syria has
about 14,000 troops in Lebanon
Some of Lebanon's anti-Syrian groups have been buoyed by Security Council Resolution 1559 last September calling on foreign troops to pull out of Lebanon, a reference to Syria which keeps some 14,000 soldiers in its smaller neighbour.
International and local critics say the presence of Syrian troops and security forces makes Syria the dominant force in Lebanese politics, while the government says Syria's presence ensures stability in the country after the 1975-90 civil war.
"Every year we organise a protest because there is no real independence ... . True independence is achieved through the withdrawal of all foreign armies, especially the Syrian army and intelligence service," Tony Nasr Allah, an official in Aoun's political group, said.
"We want to liberate our country on the basis of implementing international resolutions," Janet Aoun, a marcher, said. "We want resolution 1559 implemented."
The demonstrators were joined by dozens of marchers loyal to Druze leader Walid Jumblat. Jumblat, a former civil war leader turned minister, was a key Syrian ally who fell out with Damascus in recent months.