Recent experimental studies have shown that the photocatalytic activity of zinc oxide is enhanced when doped with cerium and that these enhancements depend on the doping concentration; in particular, the highest photocatalytic activity rates have been reported for cerium concentrations in zinc oxide close to 3.00% or 5.00%. So far, there is no sufficient explanation why the maximum photocatalytic activity rates of cerium-doped zinc oxide occur for the above concentrations. The main objective of this work is to try explain the above-mentioned. For this purpose, we performed a study based on density functional theory on the effects generated on the structural and electronic properties of different cerium concentrations in zinc oxide, and found that the relative position of the fermi level (closeness to the valence band) could be related to the peaks of a higher photocatalytic activity of Zn1-xCexO. We also found that for a low cerium concentration rate, the value of the