On December 13, 1981, communist-era strongman General Wojciech Jaruzelski imposed martial law to stifle rising opposition, headed by the Solidarity movement.
It was the start of a dark chapter in modern Polish history that saw thousands of opposition activists jailed and dozens killed.
President Andrzej Duda was on Friday expected to hand out state decorations to former anti-communist opposition activists during a ceremony in Warsaw.
Later in the day, a religious service was due to be held at the former Rakowiecka Prison in the Polish capital to honour the victims of the communist-era crackdown.
According to a parliamentary report compiled at the start of the 1990s, more than 90 people were killed during martial law, which lasted formally until July 22, 1983.
On the night of December 13, 1981, more than 6,500 opposition activists were arrested and interned.
During martial law Poland’s communist regime suspended political and workers’ organisations and introduced a curfew.