In this article we present new data of a sample of core-collapse supernovae showing unequivocal evidences of interaction between their ejecta and pre-existing circumstellar matter (CSM). This CSM was produced by the progenitor star through major mass loss episodes during the final stages of its life. The study of the properties of the SN ejecta and the circumstellar environment are crucial to unveil the nature of the progenitors producing interacting supernovae. In this context, the instrumental combination Very Large Telescope (VLT) plus X-shooter provides spectra covering simultaneously the optical and near-infrared domains, and with adequate resolution to constrain the main properties of the supernova and its environment, including its chemical composition, the ejection velocity and the distribution of the emitting gas.Based on observations collected at the European Southern Observatory, ESO, the VLT/Kueyen telescope, Paranal, Chile, proposal codes: 084.D-0265(A), 085.D-0701(A), P.I. S. Benetti.