In a centrifugal rotor having inlet channels (23) which are situated between a stack of axially separated conical separation discs (13) and the rotor end wall (10), against which the separation discs turn their apex ends, there is formed a counter pressure chamber (22) in an area where the inlet channels (23) communicate with one end of several distribution channels (21) extending through the stack of separation discs. The counter pressure chamber (22) is free of entrainment members, so that liquid leaving the inlet channels (23) is allowed to rotate in the counter pressure chamber at a smaller angular speed than the rotor. Furthermore, the counter pressure chamber (22), communicates with a radially outer part of the rotor separation chamber (9) through a space (35) situated outside a flow space (36), through which separated liquid is to flow from the interspaces between the separation discs to a number of outlet channels (27) in the vicinity of said rotor end wall (10).