A high degree of local ordering of isomorphous cations, determined by a great difference in their effective charges, was found in stoichiometric CrNbO₄ and LiFeO₂ oxides. The character of the ordering (one-dimensional in CrNbO₄, supposedly approaching the AlWO ₄ type, and two-dimensional in LiFeO₂ with a symmetry decreased to tetragonal and approaching the CuAu type) depends on the anisotropy of cation distribution in the cation coordination spheres. Microdomains with an almost complete ordering inside one block of the crystallite mosaic may develop in LiFeO₂.