Aspects relate to methods for processing individual spectra acquired with a time-of-flight mass spectrometer to form a sum spectrum. The peak position of a peak and its total intensity are determined in an individual spectrum, and entries in an addition raster of the sum spectrum adjacent to the peak position are selected; then the total intensity is divided up into portions, wherein more of the total intensity is added to entries which are closer to the peak position than is added to entries which are further away from the peak position.