By means of Mössbauer effect spectroscopy, ultrafine cobalt-ferrite particles was studied. The spectra were obtained between 14 K and 300 K, and also at 5 K with 4 T applied external magnetic field. The spectra obtained with large magnetic fields demonstrated the non-collinear magnetic structure occurs in the surface layers of the Co-ferrite system. The importance of the applied field during the measurements for a correct characterization and the coating effect were shown. The measurements illustrated that coating the surface of CoFe2O4 particles with oleic acid does not necessarily explain the canting of spins observed.