Desulfurization of flue gases by wet magnesium method is an economically attractive, waste-free alternative to lime-based technologies. In the years 1990-2000 ten installations were constructed on boilers of 5-92 MWt in Poland. The facilities developed the original process developed by the Technical University of Warsaw. Operation of installations proved assumed technological parameters and high quality of magnesium sulfate - a fertilizer generated as by-product of desulfurization process. In course of optimization, a version of the methos has been developed for large power production units. It was proved that desulfurization of flue gases by wet magnesium method developed by the Technical University of Warsaw instead of increasing the energy production costs, may generate profit.