Room temperature X-ray photoelectron spectroscopy (XPS or ESCA) has been employed to investigate pure single crystals of yttrium aluminum perovskite (YAlO3 (YAP)) and YAlO3 doped with several rare earth elements, Y(1-x)Ln(x)AlO(3) (Ln = Pr, Er, Ho). XPS peak shapes of the main elements forming the YAP structure, in structures that have been doped with ions of varying oxidation states, are rationalized as a function of structural environment and the oxidation state of doping ions. The significant changes in chemical shifts and full widths at half-maximum of the signals are caused by doping and the presence of color centers. The most distinctive change in chemical shifts is observed for the O(ls) peaks. Annealing in H-2/N-2 atmosphere (1200 degrees C) changes the color of the sample, removing color centers due to relocation of oxygen ions in the structure. Although the total amount of oxygen in the samples does not change, the relative ratio of oxygen ions occupying two independent positions in the structure changes on annealing. Only in the case of YAlO3 without color centers is the composition of crystal close to the stoichiometric one. Also the Y(3d) and Al(2p) signals are shifted to higher binding energies for doped YAP crystals.