The six were found guilty of "murdering four people with the aim of carrying out an initiation ritual into a sect and of desecrating the bodies of the dead," a court in the city of Yaroslavl, north-east of Moscow, said in a statement.
The group, four of whom were minors at the time, killed the four teenagers in June 2008, prosecutors said. They then desecrated the bodies and stole their possessions.
The dismembered bodies of the teenagers were found buried in the forest in August that year.
All six were found guilty of murder, while four were found guilty of desecrating the victims' bodies. The longest sentence of 20 years went to the man named as the group's leader, Nikolai Ogolobnyak.
The members of the gang called themselves Satanists and earlier carried out animal sacrifices, Komsomolskaya Pravda, the Russian daily, reported, citing investigators.
They stabbed the victims and then dismembered their bodies and cooked and ate some body parts, Komsomolskaya Pravda reported.
The four minors received the maximum possible sentence for murder, 10 years, a prosecutor, Tatyana Rachinskaya, said after the sentencing, Interfax reported.
The crimes were "revolting" and "inhumane", Ms Rachinskaya said.
Another member was convicted of murder but pronounced insane and sentenced to compulsory psychiatric treatment.
The court hearings were held behind closed doors due to the horrific nature of the crimes and because of the involvement of minors.
