The generation of runaway electrons (REs) is a significant problem in tokamak installations, causing energy loss, and melting and vaporization of the walls of the vacuum chamber. The wide deployment of Cherenkov-type detectors, in addition to other methods, is routinely used to detect high-energy electrons. This paper focuses on the cathodoluminescence and Cherenkov radiation excited in different crystals by REs. The spectral energy density of Cherenkov radiation in CaF₂ (fluorite) and diamond at various initial electron energies is calculated, taking into account the ionization losses of electron energy, the dispersion of the refractive index of these substances, and the electron energy distribution of the beam.