For a number of crude oils and resins and asphaltenes isolated from them, EPR has been used to measure the concentrations of vanadyl complexes and asphaltene paramagnetic centres and also the spin-spin and spin-lattice relaxation times of asphaltene paramagnetic centres. The spin-spin and spin-lattice relaxation times were determined by means of continuous saturation under rapid flowrate conditions. On the basis of the data obtained, a model is proposed in which plane molecules of vanadyl complexes form associates with asphaltene molecules having plane polyaromatic fragments. In this case diamagnetic complexes are formed with some asphaltene paramagnetic centres, which explains the dissimilar ratio of vanadyl and asphaltene paramagnetic centres in the oil.