With 100% of the ballots counted, Yanukovych garnered 35.32% and Tymoshenko took 25.05%.
Ex-National Bank head Serhiy Tyhypko gained 13.06%. He was followed by ex-parliamentary speaker Arseniy Yatsenyuk with 6.96% and incumbent president Viktor Yushchenko with 5.45%. A total of 2.2% of voters voted for "none of the above."
"This is preliminary information," deputy Central Election Commission chairman Andrey Magera said, adding that the official results would be made available later.
Turnout was 66.7%, sharply down from the 75% of the 2004 polls.
Both Yanukovych and Tymoshenko have indicated a desire to better relations with Moscow, soured in recent years over Kiev's NATO bid, gas disputes, and a host of other issues.
In line with Ukraine's legislation, a runoff takes place if none of the candidates is able to gain 50% plus one vote in the first round.
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Putting principles before profits