Nine candidates are running for the Serbian presidency but only two of them are seen as serious contenders - the West-leaning incumbent president, Boris Tadic, and his pro-Russian opponent, Tomislav Nikolic who is the leader of the nationalist Serbian Radicals party.
Under existing legislation, the winner must gain more than 50% of the votes to become president.
Both Tadic and Nikolic are strongly opposed to Kosovo's independence but Nikolic has promised a tougher stance on relations with the European Union, if it recognizes the breakaway province's statehood.
The Albanian-dominated Serbian province of Kosovo has been a UN protectorate since the NATO bombing of the former Yugoslavia ended a conflict between Albanian and Serb forces in 1999.
Most Western states back the volatile area's drive for independence, and recently agreed that Kosovo's status would be determined by the European Union and NATO. Russia insists that Belgrade and Pristina continue to seek a compromise.
Kosovo's newly elected Prime Minister Hashim Thaci earlier said Pristina's independence was an accomplished fact and would be declared as soon as the United States and the European Union were ready to recognize it.