CAR ex-PM Touadera ahead after election
He was prime minister in the government of ex-President Francois Bozize, ousted in 2013 by mainly Muslim Seleka rebels.
Voting took place on 30 December, with UN troops guarding polling stations.
Thirty candidates vied to replace interim leader Catherine Samba-Panza in the former French colony.
CAR has been torn by sectarian violence since the Seleka rebels seized power in March 2013.
A band of mostly Christian militias, called the anti-Balaka, then took up arms against the Seleka.
Strong lead
Mr Touadera, 58, was a university maths lecturer before entering politics. He ran as an independent in the election.
With most votes counted in the capital Bangui, he is well ahead of his nearest rival, Anicet Georges Dologuele, another former prime minister.
Besides Bangui, many votes remain to be counted in CAR`s provinces, as well as those of refugees and other CAR citizens abroad.
Mr Touadera has more than 120,000 votes, while Mr Dologuele has just over 68,500.
In third place is Desire Kolingba, son of a former president, the national electoral authority says.
The interim government and international donors pushed for the poll, believing that an elected president and parliament would help CAR recover from years of unrest.
CAR is one of the world`s poorest countries - yet it is rich in natural resources.
Elections also took place for the 149-seat National Assembly.
After seizing power, the Seleka rebels installed Michel Djotodia as the first Muslim leader of the majority Christian country.
But under pressure from regional leaders and former colonial power France, Mr Djotodia stood down and was succeeded by Ms Samba-Panza.
About 1.8 million people were registered to vote, out of a population of roughly five million.
More than one million people fled their homes during the intercommunal fighting.