We present results from beam tests performed in 2007 on PbWO₄ and BGO crystals in the context of the DREAM project. Signals from high energy electrons and pions are analyzed and the possibility of separating the contributions from Čerenkov (C) and scintillation (S) light for individual events is investigated. Different methods exploiting the difference in timing, in the spectra and in the directionality of the two types of light have been developed to determine the contribution of the two components. In the BGO crystal, Čerenkov signals have been enhanced with the use of optical filters and the ratio Č/S is measured with good precision (∼20-30% for energy deposits less than 1 GeV).