The Polish state agency says Jaroslaw Kaczynski, the twin brother of Poland's late President Lech Kaczynski, will run for president.
PAP gave no source for its report.
Kaczynski will be the candidate of the right-wing Law and Justice Party (PiS) which he currently leads in the election set for June 20.
He was expected to announce his decision later today.
The candidate of Poland's centrist ruling Civic Platform, Bronislaw Komorowski, is currently favoured to win the ballot.
compiled from agency reports