Reactive absorption using aqueous amine solutions is the technically most feasible retrofit option for the separation of CO2 from flue gases. Frequently discussed issues are the realization of a cost-effective increase in efficiency in the sophisticated overall absorption process and the minimization of the energy demand for solvent regeneration under operating conditions. However, the influence of degradation phenomena on capacity and energy efficiency during the absorption-regeneration cycles using blended monoethanolamine solutions has been less considered so far. The decrease in capacity depends in particular on time, temperature, O-2- and SO2 concentration in the flue gas and has to be considered in plant design. Addition of degradation inhibitors decreases the energy requirements.