A series of carbamate and phenylurea pesticides was studied by ion-trap MS/MS collision-induced dissociation (CID) in the resonant excitation mode. CID mass spectra contained highly abundant daughter ions formed by simple cleavage as well as by rearrangement processes. The formation of rearrangement daughter ions vs. cleavage daughter ions was found to be dependent on the CID voltage and CID time in some of the investigated compounds. The relative intensity of the ions formed by cleavage, i.e. via high-energy pathways, vs. ions formed through rearrangement processes, i.e. via low-energy pathways, increased with increasing collision energy. A similar effect was obtained by increasing the CID time, thus enabling the ions to gain more energy and consequently form more cleavage ions than rearrangement ions.