EN
In this paper we present the results of ESR and photo-ESR measurements on YAlO_{3}(YAP) single crystals and powder samples doped purposely with about 1 at.% Nd^{3+} and undoped crystals in which Er^{3+} was observed as residual dopant. The ESR measurements were carried out at X-band spectrometer in 4-300 K temperature range. The photo-ESR was performed at 5 K using a mercury arc lamp. For the Nd^{3+} doped crystals the intensity of ESR signal decreased about 2 times during illumination conditions. Moreover, the calculations of the g tensor and A hyperfine structure parameters for Nd^{3+} and Er^{3+} were carried out.