A rotor for an axial flow turbomachine is provided. The rotor includes a plurality of rotor discs that are arranged in stacks and clamped together with at least one tie rod. At least one of the rotor discs of the rotor comprises a smaller outer diameter than one of the neighboring rotor discs and that the difference in diameter is compensated by a drum surrounding the rotor disc with the smaller outer diameter as a ring. The drum may be made of a heat resistant material. The rotor discs surrounded by the drum may be made of a less expensive material. Furthermore, the drum may include at least one more blade ring than the rotor discs that are surrounded by the drum.