More than 200 engineers and mechanics are now working on the khaki-painted tanks at a specialised repair factory just outside the northwestern city of Saint Petersburg.
Due to be fully restored by late March, they will roll across Red Square on May 9 in a special extended military parade to mark 75 years since the Allied victory over the Nazis, watched by world leaders including French President Emmanuel Macron.
The tanks sent from Laos were built in the 1950s in Soviet-bloc Czechoslovakia. Laos reportedly acquired them in 1987 from Communist ally Vietnam, where they were used in the war with the United States.
The powerful and manoeuvrable T-34 tanks were a Soviet workhorse and particularly significant for their role in World War II, with more than 58,000 built between 1940 and 1946, and seen as key in the USSR's military defeat of Nazi Germany. "The T-34 was the weapon of victory, the main weapon that helped us to conquer our enemy," said Roman Chepurnov, director of Tank Repair Factory No 61, part of the Uralvagonzavod group that makes tanks and armoured vehicles.
Now, though, they are a rarity in Russia, since many were remodelled after World War II or scrapped.