The invention concerns a gas and steam turbine plant comprising a waste heat steam generator (6) which is arranged downstream of the gas turbine (2) on the exhaust gas side and whose heating surfaces are connected into the water-steam circuit (8) of the steam turbine (4) which comprises a high-pressure section (4a), a medium-pressure section (4b) and a low-pressure section (4c). According to the invention, in order for the plant to attain the highest degree of efficiency, a heat exchanger (70) is disposed on the primary side outside the waste heat steam generator (6) between the high-pressure section (4a) and the medium-pressure section (4b) and on the secondary side between the medium-pressure section (4b) and the low-pressure section (4c) of the steam turbine (4). In a corresponding method of operating a plant of this type, low-pressure steam (ND) flowing towards the steam turbine (4) is heated by indirect heat exchange with medium-pressure steam (MD) flowing out of the steam turbine (4).
