KIEV, Jan. 17 (Xinhua) -- Ukrainian voters go to the polls on Sunday to choose their next president from a list of 18 candidates.

    It is the first general election since the 2004 "Orange Revolution" which led to a re-run poll that was won by Viktor Yushchenko.

    The Ukrainian president is elected for a five-year term under atwo-round voting system. If no candidate gains more than 50 percent of the vote in the first round, then a run-off will be held between the two candidates with the highest number of votes.

    Opinion polls show that Viktor Yanukovych, head of the leading opposition Regions Party, and Prime Minister Yulia Tymoshenko are two front runners.

    Yanukovych was born in July 1950. During 1997-2002, he served as governor of Donetsk Oblast in eastern Ukraine. He lost the re-run poll to his main rival Yushchenko during the last presidential elections and came back in 2006 when Yushchenko appointed him prime minister after the Regions Party formed a coalition with other parties in parliament.

    As no candidate is likely to win outright in Sunday's election, Yanukovych and his main rival Tymoshenko are expected to enter thesecond round scheduled for Feb. 7.

    Tymoshenko was born in November 1960. She graduated from Dnipropetrovsk State University with a degree in economics in 1984. She was appointed deputy prime minister in charge of energy in 2000.

    During the 2004 "Orange Revolution," she was allied with Yushchenko. Tymoshenko became Ukraine's first female prime minister in 2005, but was sacked by Yushchenko before long. She was appointed for a second time in December 2007. The two are now deadly rivals.

    Sergey Tigipko, head of the "Strong Ukraine" party, was born inFebruary 1960. He was head of Ukraine's central bank during 2002-2004 and oversaw the election campaign in 2004 for presidential candidate Viktor Yanukovych. Tigipko, who has called for structural reforms in all economic sectors, has seen his popularity rise rapidly in the past three months.

    Yushchenko, the incumbent president, was born in northern Ukraine in February 1954. He graduated from the Ternopil Finance and Economics Institute in 1975 and was appointed in 1993 and re-appointed in 1997 chairman of the National Bank of Ukraine.

    In December 1999, he was chosen as prime minister and became president after the "Orange Revolution." But his support has ebbed away since 2004 and has little chance of winning a second term in office, according to opinion polls.