EPR spectra of iron oxides, obtained by calcination of iron oxide-hydroxides alpha-, beta-, gamma- and delta-FeOOH, and ruthenium catalysts based on them (Ru/Fe2O3 and Ru/Na-Fe2O3), used for the water-gas shift reaction (WGSR), were analyzed. The iron oxide (B) (obtained from beta-FeOOH) is inactive in WGSR. Deposition of ruthenium on iron oxide supports, in particular on those modified with sodium, enhanced the electron exchange.