In SIMS, the emission of negative secondary ions is strongly enhanced by the introduction of electropositive elements into the system. In our group, we have extensively studied SIMS analyses either performed with simultaneous cesium (Cs) deposition or with Cs deposition prior to the analysis. These studies were mainly performed on inorganic samples, focusing both on steady-state and pre-equilibrium conditions. The interest of Cs deposition prior to the SIMS analysis has been presented for inorganic as well as organic samples on the Cameca Sc-Ultra and NanoSIMS50 instruments. The present work has been carried out on different organic samples including PTCDA and C60, which were covered with a layer of Cs prior to SIMS analysis. The diffusion of Cs into the sample as well as the change in emission of positive and negative secondary ions have been monitored by SIMS depth profiling by using Cs+ primary ions. Furthermore, the effect of air exposure on the obtained results has been investigated. The study on the same organic samples is completed by Cs deposition performed simultaneously to primary ion bombardment. Copyright © 2012 John Wiley & Sons, Ltd.