[en] A magnetic resonance method is applied to the investigation of a number of isostructural diamagnetic compounds ABO₃ (A = Sc, In, and Ga) with small additions of Cr³⁺ ions (S = 3/2) sufficient to observe single-ion and pair spectra. It is shown that the resonance spectra for isolated Cr³⁺ ions can be described to a good accuracy by the ordinary axial spin Hamiltonian for 3d ions in octahedral oxygen environment. The parameters of the spin Hamiltonian are determined for single Cr³⁺ ion and Cr³⁺–Cr³⁺ pair. Lattice distorsions of the parent ABO₃ crystals caused by the Cr³⁺ impurities is discussed.