Evolution of ESR spectra upon irradiation in the course of photoselection and photo-orientation has been investigated experimentally and by numerical simulation. Light-induced angular dependence of spectra has been considered. The quantitative characteristics of the light-induced orientation degree for paramagnetic species an suggested. The alignment of paramagnetic species was shown to depend on Light absorption anisotropy, a maximal alignment being achieved upon irradiation with both polarized acid unpolarized light. The values of orientation degree, which can be experimentally achieved, are determined, and the reasons for their decrease in comparison with those theoretically predicted are discussed. The possibilities of the method suggested for estimation of the transition dipole moment by ESR investigation of photoselected samples are demonstrated.