Methods are provided for acquiring sum spectra in a time-of-flight mass spectrometer with orthogonal pulsed acceleration, where each of the sum spectra is obtained from a plurality of summed individual spectra. The mass spectrometer has an ion storage device that collects the ions temporarily before they are transferred to an ion pulser, which pulses out the ions orthogonally. Acquisition conditions such as, for example, delay times between opening the ion storage device and the pulsed ejection in the ion pulser are varied for the individual spectra, which are added together to form the sum spectrum of ions with light masses and high masses.