Russian prime minister Vladimir Putin and his Polish counterpart Donald Tusk are to lay the cornerstone of a new Russian orthodox church at the site of the massacre in Katyn, in western Russia. It is the first time that a Russian leader has publicly commemorated the event.
The Polish victims were captured by Stalin's Red Army after leaving their country following Hitler's September 1939 invasion of Poland. Russia did not acknowledge the massacre had taken place until nearly 50 years after the event.
World War II is still a source of tension between Russia and Poland. Under Boris Yeltsin, Russia released documents showing that Stalin’s Politburo directly ordered the massacre, but many people in Poland have demanded that Putin apologise publicly for the murders.
Last year, in the lead up to the 70th anniversary of the beginning of the war, Russia criticised Poland's war record. Russian media claimed Warsaw had intended to collaborate with Hitler in an invasion of the Soviet Union, and that Poland's foreign minister in 1939, Jozef Beck, was a German agent.
There were also suggestions that the Germans were involved in the Katyn slaughter, rankling Poles, who have long complained that Russia has failed to take full responsibility.
Putin wrote to Polish newspaper Gazeta Wyborcza last year, taking a conciliatory tone.
"Our duty is to remove the burden of distrust and prejudice left from the past in Polish-Russian relations," he wrote. He also thanked the Poland for the 600,000 soldiers who fought on the Eastern Front under Red Army command.
Putin and Tusk will also commemorate Soviet victims of Stalinist terror campaigns.