Large argon cluster ions can very successfully be applied as primary ion projectiles in SIMS, but until recently, these sources could not be used in combination with conventional TOF-SIMS systems. The large cluster size distribution limited the possibility to pulse the primary ion beam, which is a prerequisite for high mass resolution surface spectrometry. We developed a unique 90° pulsing system which enables the generation of short primary ion pulses for high mass resolution surface spectrometry. The pulsing system allows the variation of the applied cluster size from 250 to 10000 atoms/cluster. In this contribution, we present and compare data about the influence of the cluster size on the spectra appearance, the fragmentation and the secondary ion yield on different organic sample systems. Copyright © 2012 John Wiley & Sons, Ltd.