Two different parameterizations of the semi-empirical method of the intermediate neglect of the differential overlap (INDO) are applied to the calculations of the small-radius hole polarons in the corundum (α-Al2O3) crystal. The 80-atom supercell has been used for the study of the atomic and electronic structure of a free small-radius hole polaron (the self-trapped hole, STH) and a hole polaron bond by a Mg impurity (the so-called VMg centre), respectively. Both parameterizations indicate that he two-site (quasi-molecular) configurations of both kinds of polaron have the lowest energy (which does not exclude the existence of one-site polarons also characterized by considerable relaxation energies). For VMg centres, the lower energy is calculated for the defect configuration where the Mg-ion substitution is nearest t the hole polaron. Experimental ENDOR data on VMg defects are discussed i the light of the calculations.