Abstract: The power production process with a gas turbine where as primary power source solid fossil fuels, alternative fuels and wastes at their combustion with air or oxygen can be utilized. The operating medium is the steam-gas mixture of gas supplied by a compressor (22) and of steam of the cooling medium of the cooled combustion chamber (1), whereas the injected medium is injected into the gas forwarded by means of the compressor (22) before the compressor (22) or before the heater (7) of the steam-gas mixture or at least between some parts of the heater (7). The gas turbine (28) can be utilized in connection with a regeneration exchanger or with the installation of the Rankine-Clausius steam cycle utilizing the waste heat of flue gas from the gas turbine (28).