Bosnian Serb leader Radoslav Brdjanin, who helped run a Serb region in north-western Bosnia during the war, has had his sentence cut by two years.
Mr Brdjanin had his sentence cut to 30 years
It came after an appeal against the original 32-year sentence by the International War Crimes Tribunal.
The appeals panel at the tribunal in The Hague struck two elements off Brdjanin's conviction, but upheld all eight of the main charges.
These included charges of persecution and torture.
The appeals court reversed his convictions for aiding and abetting torture in detention camps and for the wanton destruction of cities and other settlements.
Brdjanin, 59, had challenged hundreds of the court's findings in his appeal.
At his trial in 2004, judges said he bore heavy responsibility for the deaths of more than 1,600 Muslims and Croats killed during the ethnic cleansing of territory captured by Serb forces.
Judges said Brdjanin authorised the torture and forcible deportation of non-Serbs at the start of the conflict.
He is also said to have turned a blind eye to atrocities at several camps, TV footage of which caused international outrage.
Brdjanin was a prominent member of former Bosnian Serb leader Radovan Karadzic's hardline Serb Democratic Party, backing a plan to drive ethnic Croats and Muslims from parts of Bosnia by force before his resignation from the party in 1994.
The latest judgement from the tribunal cannot be appealed.