A combined combustion and steam turbine power plant which includes a steam turbine unit, a boiler unit for supplying steam to the steam turbine unit, and a combustion turbine unit with an exhaust gas duct structure for supplying the turbine exhaust gases to the boiler unit, has at least one heat recovery steam generator arranged in the exhaust gas flow downstream of the boiler unit and connected to the steam-turbine unit so as to supply any steam generated in the heat recovery steam generator to the steam turbine unit.