The efficiency of X-ray-induced scintillation in glasses roughly depends on both the effective atomic number Zeff and the photoluminescence quantum efficiency Qeff of glass, which are useful tools for searching high-performance phosphors. Here, we demonstrate that the energy transfer from host to activators is also an important factor for attaining high scintillation efficiency in Ce-doped oxide glasses. The scintillation intensity of glasses with coexisting fractions of Ce3+ and Ce4+ species is found to be higher than that of a pure-Ce3+-containing glass with a lower Zeff value. Values of total attenuation of each sample indicate that there is a non-linear correlation between the scintillation intensity and the product of total attenuation and Qeff. The obtained results illustrate the difficulty in understanding the luminescence induced by ionizing radiation, including the energy absorption and subsequent energy transfer. Our findings may provide a new approach for synthesizing novel scintillators by tailoring the local structure.