Millions of Poles are heading to vote in a runoff presidential election that surveys show has no front-runner.
Incumbent Bronislaw Komorowski finds himself neck and neck with his conservative challenger, Andrzej Duda, who narrowly won the first round held on May 10 but failed to pass the 50 percent mark.
A victory by Duda, 43, would be the first major electoral win in nearly 10 years for the opposition Law and Justice party as Komorowski's center-right Civic Platform party has governed the country for the past eight years.
The prime minister leads the government in Poland but the president is head of the armed forces, has a say in foreign policy, can veto legislation, and controls the central bank.
Komorowski, 62, has been criticized for running a lackluster campaign and is scrambling to be reelected despite ruling during a period of rapid economic growth and growing salaries in Eastern Europe's largest economy.
Exit polls are to be published after voting ends in the evening, but final results are not expected until May 25 at the earliest.