Polling stations opened at 5:00 am (0400 UT/GMT) across the country and will remain open until 5:00 pm.
Some 40 million registered voters will choose a successor to President Joseph Kabila, who is stepping down two years after his term limit expired.
RFI correspondent Kamanda Wa Kamanda, reporting from a polling booth at the Institute of Commerce in Kinshasa, said voting had begun smoothly in the capital in the early hours.
In North Kivu, residents of Beni improvised their own polling station, despite the postponement of the election in the region, with authorities citing health and safety concerns over the Ebola outbreak.
Voting was delayed in the cities of Beni and Butembo – but not in other communities hit by the haemorrhagic fever – until March, long after the scheduled inauguration of Kabila's successor in January.
Critics see the move as a move by the government to suppress the vote in opposition strongholds.
Several technical problems have also been reported across the country, causing delays.
Hours after voting began in the capital, correspondent Florence Morice, at the Malula Foundation, said polling booths had not yet been set up.
Dozens were forced to wait outside in the rain for hours, as voting lists had not been delivered.
"We have not been told anything," one voter tells RFI. "It seems there are no lists (...) We want to see the lists ".
For him, this election is crucial: "It's for the Congolese nation. It's really very important. We must vote. We need a new leader for the country to move forward," he says.
DRC has never seen a peaceful transition of power since it gained independence from Belgium in 1960.