The Moscow City Court has announced a two-year reduction in the prison sentences for former oil tycoon Mikhail Khodorkovsky and his business partner, Platon Lebedev.
On December 20, the court cited changes in Russian laws on economic crimes.
Both were convicted of evading taxes and for stealing oil from the Yukos oil company and laundering the proceeds.
The decision means both could be released in 2014.
Before his arrest, Khodorkovsky was seen as a potential political player in Russia.
Russian President Vladimir Putin was asked about the Khodorkovsky case during the first news conference of his third presidential term on December 20.
Putin said that "everybody seeks to portray Khodorkovsky's case as a political one," but stressed that he was sentenced "purely" for economic crimes.
With reporting by AP, Reuters, and RFE/RL's Russian Service