The invention relates to a method for removing solids in dust and sulphur oxides from process gases generated in a metallurgical process by a wet process. At least part of basic liquid is fed into the gas flow containing solids in at least one cascade scrubber in order to mix basic liquid with the gases and solids to be cleaned at the latest during the wetting of the gases and solids in the water space of the cascade scrubber, and the mixture containing basic liquid, wetted gases and solids are directed to have a cascade shower in each cascade scrubber in order to remove sulphur and solids from the gases.