The white-bearded Lizcano, who escaped his captors three days before being found, looked haggard in a grimy black shirt and muddy pants when he spoke to reporters at a brief news conference at a military base in the western city of Cali.
He apologized for his somewhat incoherent speech and thanked "the person who had the courage, the valor to leave with me."
"I was really sick," he said, seated in a chair beside Defense Minister Juan Manuel Santos and police and military commanders. He said he had eaten little while on the run with his 28-year-old captor, known only by the alias "Isaias" or "Isaza."
Lizcano was then taken to a clinic for medical tests.
Santos said the escape followed the Oct. 10 desertion of a second rebel, alias "Moroco," from the camp where Lizcano was being held. He said that guerrilla had disclosed Lizcano's whereabouts to authorities, who cut off supply routes to the rebels holding Lizcano. Santos put their number at about eight women and six men.
Colombia's military has in recent months put withering pressure on the guerrillas known as the FARC, killing or capturing top commanders and spurring record desertions and betrayals among rebels with lucrative reward offers. Santos said authorities were studying whether to pay "Isaias" a reward.
Upon being told earlier Sunday that her husband was free, Martha de Lizcano wept.
"It's been eight years of great suffering," she told Caracol radio.
Lizcano was kidnapped on Aug. 5, 2000. The government's peace commissioner, Luis Carlos Restrepo, had said last week without providing details that FARC deserters had reported Lizcano's health was delicate.
The rescue comes nearly four months after Betancourt, a dual French national, and the three Americans were freed in a sophisticated ruse engineered with the help of a rebel turncoat in which Colombian military agents posing as humanitarian workers helicoptered 15 FARC-held hostages to freedom without a shot being fired.
Informed of Lizcano's freedom, Betancourt told Caracol radio that it should send a message to the rebels that "it should change its attitude, that we should get a peace process going in Colombia."
Efforts to negotiate a prisoner swap were frozen months before her rescue and the government has said it has made no efforts to contact the rebels and resume them.
In April, the FARC released a so-called "proof-of-life" video of Lizcano in which he pleaded with Venezuelan President Hugo Chavez to do "the utmost to get us out of here because we are rotting in the jungle."
The FARC still holds at least 20 high-value politicians, police officers and soldiers - including a provincial governor and a police colonel, some of whom have been held for more than a decade.
It has been seriously weakened in the past two years - down to an estimated 9,000 fighters by government count - by a military that has been fortified and become more professional and agile under Uribe thanks in considerable measure to U.S. training, advising and intelligence-gathering.
Associated Press writer Frank Bajak contributed to this report.