A rotary pump, preferably a vane cell pump or a pendulum slider pump, comprising (a) a stator and (b) a rotor which can rotate about a rotational axis within the stator, wherein (c) the rotor comprises multiple delivery elements which can move radially in relation to the rotational axis, and (d) two adjacent delivery elements limit a delivery cell (11 to 13, 21 to 26) together with the outer surface area of the rotor and the inner surface area of the stator, wherein (e) at least two adjacent delivery cells (11 to 13) which exhibit a first maximum cell volume form a first delivery cell group and (f) at least two other adjacent delivery cells (21 to 26) which exhibit a second maximum cell volume form a second delivery cell group (g) and optionally another at least two other adjacent delivery cells which exhibit a third maximum cell volume form a third delivery cell group, wherein (h) the first maximum cell volume of the delivery cells (11 to 13) of the first delivery cell group is larger than the second maximum cell volume of the delivery cells (21 to 26) of the second delivery cell group, and the second maximum cell volume is larger than the third maximum cell volume, if the third delivery cell group is provided, and (i) the delivery elements which limit a delivery cell (11 to 13) of the first delivery cell group are each arranged at a first angular distance (α) from each other on the rotor, and the delivery elements which limit a delivery cell (21 to 26) of the second delivery cell group are each arranged at a second angular distance (β) from each other on the rotor, wherein the first angular distance (α) is larger than the second angular distance (β), characterised in that (j) the rotary pump contains only delivery cells which are assigned to the first delivery cell group or to the second delivery cell group or to the third delivery cell group, if provided. (a) a stator and (b) a rotor which can rotate about a rotational axis within the stator, wherein (c) the rotor comprises multiple delivery elements which can move radially in relation to the rotational axis, and (d) two adjacent delivery elements limit a delivery cell (11 to 13, 21 to 26) together with the outer surface area of the rotor and the inner surface area of the stator, wherein (e) at least two adjacent delivery cells (11 to 13) which exhibit a first maximum cell volume form a first delivery cell group and (f) at least two other adjacent delivery cells (21 to 26) which exhibit a second maximum cell volume form a second delivery cell group (g) and optionally another at least two other adjacent delivery cells which exhibit a third maximum cell volume form a third delivery cell group, wherein (h) the first maximum cell volume of the delivery cells (11 to 13) of the first delivery cell group is larger than the second maximum cell volume of the delivery cells (21 to 26) of the second delivery cell group, and the second maximum cell volume is larger than the third maximum cell volume, if the third delivery cell group is provided, and (i) the delivery elements which limit a delivery cell (11 to 13) of the first delivery cell group are each arranged at a first angular distance (α) from each other on the rotor, and the delivery elements which limit a delivery cell (21 to 26) of the second delivery cell group are each arranged at a second angular distance (β) from each other on the rotor, wherein the first angular distance (α) is larger than the second angular distance (β),