Abstract: A combined cycle power plant has his power output augmented by addition of a gas turbine (GT1) with a dedicated heat recovery steam generator (HRSG1). Steam produced by said heat recovery generator (HRSG1) is injected in the combustion chamber of the combined cycle plant. In this way the combined cycle plant power is augmented by the power of the additional gas turbine plus two further contributions due to steam injection. The first contribution is given by the increased flow rate through the gas turbine (GT) of the combined cycle plant. The—second contribution is given by the said increased flow rate flowing also through the heat recovery steam generator (HRSG) of the combined cycle plant, hence increasing the thermal power available herein and causing an increased power output at the steam turbine (ST).