Cs-promoted Ru-Na/SiO2 catalysts were characterized via H-1 NMR spectroscopy. Contrary to the results of studies using single crystals, we did not find any evidence of a ruthenium-mediated electronic interaction between the alkali promoter and adsorbed hydrogen. The site blocking effects of the Cs promoter diminished after exposure to hydrogen for extended periods of times. This effect was partly reversible after thermal evacuation of the hydrogen. In the presence of Cs, the surface of the support was also modified; the intensity of the diamagnetic resonance in the spectrum (predominantly Si-OH) decreased, and an additional resonance appeared in the spectra. There is evidence that hydrogen spillover and hydrogen mobility were also restricted in the Na-Cs-promoted system.