The theoretical limit of the cathodoluminescence efficiency for crystallophosphors is 30-35% [1]. This is defined by the fact that at electronic excitation of a semiconductor the energy needed to produce an electron-hole pair approximately by a factor of three exceeds the energy gap. The efficiency of known cathodoluminophores does not exceed 25%, and this limit could not be improved during the last 40 years [1-3]. The peculiarities of the structure of quantum dots [4,5] and their optical properties allow one to expect that the cathodoluminescence efficiency of quantum dots can be increased. The dimensions of grains in crystalline phosphors usually are not less than 1-5 μm. At the optimal surface density of the luminophore, which theoretically ensures the maximal light intensity, only ~90% of the substrate surface is coated; hence, actually the screen brightness in by 10% less than the maximal attainable value [2]. Dimensions of quantum dots are of the order of nanometers. This allows one to prepare luminophore layers of any thickness and to control the thickness with accuracy up to the parts of a micron with uniform distribution of the luminophore over the surface. We have tested at different conditions cathodoluminophores on the basis of various core-shell colloidal quantum dots (QDs) at excitation by an electron beam (voltage 10-25 kV and current density up to 10 μA/cm2). The multishell CdSe/CdS/CdZnS quantum dots (4-6 shells) with red emission (λmax = 600-630 nm) exhibited the greatest brightness comparable with Y2O2S:Eu emission at the same excitation conditions. They also exhibited the greatest quantum yield within the available samples (50-70%). The quantum yield of up-to-date commercial phosphors exceeds 95% at photoexcitation. For the studied red emission QDs it was not greater than 50-70%. Since even at these values of the quantum yield the brightness of QD luminophores was comparable with the commercial red Y2O2S:Eu phosphor, one can suppose that improvements of the QD synthesis methods, increasing of the quantum yield up to 0.9 or greater values, and some other innovations will allow one to create cathodoluminophores with greater efficiency. Luminophores on the basis of quantum dots are promising, since they in principle allow one to prepare composites with the specified spectrum in a wide range from 300 to 2000 nm even using the up-to-date manufacturing technology. Application of composite luminophores, which combine crystalline phosphors and quantum dots, is also possible.