In a decanter centrifuge having a rotor (1) and a screw conveyor (2) the rotor is suspended only at its one end, the rotational axis (R) of the rotor extending vertically. The inlet (22) of the rotor (1) for a sludge containing liquid to be separated as well as the rotor outlet (12; 67) for liquid having been freed from sludge are situated at the upper end of the rotor, whereas a sludge outlet (13) for separated sludge is situated at the lower end of the rotor. The rotor (1) as well as the screw conveyor (2) are adapted to be driven through shafts (5, 8) situated at the upper end of the rotor. By the invention it becomes possible by simple means to adapt the decanter centrifuge for different separation duties, since the location of the sludge outlet (13) can be chosen freely without other parts of the decanter centrifuge preventing this.