Abstract: The invention relates to a method for renewed activation of honeycomb-shaped catalyst elements for denitrating flue gases from fossil fuel-fired boiler plants, specially coal-fired boiler plants in large power stations. According to the invention, each catalyst element if mechanically cleaned using oil and water-free compressed air before mounting. Subsequently, each element is subjected to wet chemical cleaning using fully desalinated water and dried with oil and water-free compressed air. The inventive method enables the activity of used catalyst elements to be increased from less than 50% to more than 83% of original activity.