EPR paramagnetic probe method with 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) as a probe has been applied to study of electron-accepting properties of the surface of (Y, La 0 . 1 )Ce x Zr 1 - x O 2 - y (x=0.1-0.7), Y 0 . 1 Pr 0 . 3 Zr 0 . 6 O 2 - y and Y 0 . 1 Pr 0 . 1 5 Ce 0 . 1 5 Zr 0 . 7 O 2 - y mixed oxides. Two types of acceptor sites-coordinatively unsaturated (cus) cations Zr 4 + and Ce 4 + -have been revealed on the CeO 2 -ZrO 2 surface after thermovacuum treatment (820K). The relative amounts and ''strength'' of these centers were evaluated on the basis of EPR spectra analysis. An introduction of trivalent Y 3 + or La 3 + cations reduces the amount of electron-acceptor sites belonging to cerium cations, stabilizing ones as Ce 3 + . A formation of very strong electron-accepting sites (Pr 4 + cus cations) able to form charge transfer complexes with adsorbed TEMPO on the surface of praseodymia-containing samples after thermovacuum treatment was found out. At the same time electron-accepting ability of Zr 4 + cationic sites on Y 0 . 1 Pr 0 . 3 Zr 0 . 6 O 2 - y and Y 0 . 1 Pr 0 . 1 5 Ce 0 . 1 5 Zr 0 . 7 O 2 - y surfaces decreases in comparison with ceria-zirconia one. The generally used IR spectroscopy technique with CO as a probe molecule appeared to be considerably less informative for such systems characterization, due to their high catalytic activity to carbon monoxide. A formation of paramagnetic Zr 3 + ions in ceria-zirconia mixed oxides has been investigated by EPR spectroscopy technique. The different states of this paramagnetic ion are realized in the complex oxides depending on Ce/Zr ratio.