Donald Tusk was called as a witness to the national prosecutors office in Poland as he was PM at the time of the 2010 crash in which president Lech Kaczynski died.
Officials want to quiz him about about why Poland failed to ensure crash victims were correctly identified, after it was found some ended up buried in the wrong graves.
All 96 people on board a Polish Air Force Tupolev Tu-154 aircraft died when it came down short of Smolensk airport in Russia on 10 April 2010.
The leader of the ruling Law and Justice party, Jaroslaw Kaczynski, is the former president’s surviving twin brother.
The party returned to power in 2015 and in February last year defence minister Antoni Macierewicz ordered a new investigation into the crash, saying previous inquiries were “riddled with mistakes”.
Remains of the deceased were exhumed as part of the renewed probe.
Supporters of the European Council president chanted “Donald Tusk!” and waved EU flags as he arrived at the offices in the capital Warsaw.
A small number of anti-Tusk protesters took part in a counter demonstration, holding banners with slogans like “Smolensk murder” and pictures of Mr Tusk in a prison uniform.
Mr Tusk spoke briefly to the crowd of reporters outside. According to the se.pl website, he said: “I have to deal with this burden.”
Jaroslaw Kaczynski is a bitter political opponent of Mr Tusk and accuses him of partial responsibility for the tragedy, something Mr Tusk denies.
Since the Law and Justice Party returned to power, several of its other prominent politicians have made statements attacking Mr Tusk, including a government spokesman who called for the ex-PM to be put on trial for his handling of the aftermath of the crash.
Mr Tusk was re-elected earlier this year and is expected to preside over the European Council throughout the period of the Brexit negotiations.