The hostages were described as being weak and ill, having endured terrible conditions in captivity.
A total of 21 people were released, including 19 remaining from a group of 80 captured during a mass kidnapping on 17 September.
It is not clear when the other two were kidnapped.
The release had been negotiated as part of a ceasefire agreement signed with the government.
The hostages were described as being weak and ill, having endured terrible conditions in captivity.
They had been constantly on the run with the rebels in the mountains and in the jungle, and three died in captivity.
The ELN described the release as a "humanitarian gesture", but a BBC correspondent said that the hostages were probably freed because the guerrillas were in flight and could not hang on to them.
Ransoms sought
The hostages were restaurant-goers kidnapped in expectation of large ransoms, which the ELN uses to fund its armed campaign against the state.
The guerrillas closed in on their victims by erecting makeshift roadblocks along a stretch of highway lined with popular restaurants and weekend homes in the Andes mountains about 18km (11 miles) northwest of Cali.
About 50 armed men, many in military uniform wearing bullet-proof vests, then stormed the Cabin and Embassy of Geneva restaurants seizing the hostages.
More than 20 of the captives were freed two days after the kidnapping as the rebels tried to speed up their retreat into the mountains.
Another 12 were rescued by government forces in a military operation against the rebels a day later.
Final releases
But the release of the last group was arranged by Colombian High Commissioner for Peace Camilo Gomez and international mediators, on condition that government forces then be withdrawn from the area.
Representatives from Cuba, Spain, France, Norway and Switzerland have been monitoring the peace process with the ELN.
After monitoring the release they will oversee the troop withdrawal.
Colombia is the kidnap capital of the world, averaging more than seven a day this year.
The country has been torn apart by war between the government and several left-wing guerrilla groups.
Right-wing paramilitaries have also been targetting liberal members of parliament as kidnap victims.
About 35,000 people have been killed in the fighting since 1990.