Thin Fe, Fe2O3 and Cr2O3 films deposited on Si wafers have been investigated by grazing incidence X-ray scattering (GIXS) and the results have been compared with microstructural data by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that changes in density of these films can be estimated from the critical angle in X-ray reflection curves. Measurements in GIXS with two different geometries indicate the preferential orientation of crystalline Fe and Fe2O3 films. AFM and TEM observation shows characteristic features in microstructures of the films, and it is indicate that a ten nanometer order of magnitude of roughness in the surface prevents the oscillations in the X-ray reflection curves.