The chemical and physical processes occurring during the grinding of nickel hydroxocarbonate and mixtures of nickel hydroxocarbonate with aluminium and aluminium oxide were discussed. For mechanical treatment a planetary ball mill was used. The phase analyses of ground products were carried out using thermogravimetry and X-ray diffraction methods. The amount of Ni-2(OH)(2)CO3 undecomposed and Al2O3.xH(2)O, xNiO, Ni-o, NixAly alloys and remained Al-o in the systems strongly depends on the proportion of components and on the duration of grinding in a mill which was used in the study. The comparative results are presented.