Rare earth (RE) elements are important for the optical tuning of wide bandgap oxides (WBO) such as β-Ga2O3 or ZnO, because β-Ga2O3:RE or ZnO:RE show narrow emission lines in the visible, ultra-violet and infra-red region. Ion implantation is an attractive method to introduce dopant into the crystal lattice with an extraordinary control of the dopant ion composition and location, but it creates the lattice damage, which may render the dopant optically inactive. In this research work, we investigate the post-implantation crystal lattice damage of two matrices of wide-bandgap oxides, β-Ga2O3 and ZnO, implanted with rare-earth (RE) to a fluence of 5 x 10^14, 1 x 10^15 and 3 x 10^15 atoms/cm^2, and post-growth annealed in Ar and O2 atmosphere, respectively. The effect of implantation and annealing on both crystal lattices was investigated by channeling Rutherford backscattering spectrometry (RBS/C) technique. The level of crystal lattice damage caused by implantation with the same RE fluences in the case of β-Ga2O3 seems to be higher than in the case of ZnO. Low temperature photoluminescence was used to investigate the optical activation of RE in both matrices after performed annealing.