An attempt was made to apply the statistical analysis of NiO grain boundaries to explain the dependence of NiO growth kinetics on the crystallographic orientation of Ni substrate. Study was conducted for two crystals faces of Ni, (100) and (111), which exhibits a difference in oxidation rate constants at 1073 K, over one order of magnitude. The orientation distribution functions (ODF), calculated from X-ray measurements for NiO grown on both Ni faces, were analyzed numerically to assess the grain boundary character. The grain boundary misorientation distribution (GBMD) and grain boundary character distribution (GBCD), used to describe oxide structure, were derived using three different assumptions regarding the spatial correlation in orientation of neighbouring grains. Grain boundary network was created to analyze the high temperature diffusion properties through the oxide using diffusion constants available in the literature under assumption of various contribution of bulk and grain boundary diffusion paths to overall transport of ionic species. The growth parameters obtained were finally verified by comparison with experimentally measured oxidation kinetics.