The effects of water absorption in complexes of poly(ethylene oxide) with lithium salts (LiClO4, LiBF4 and LiAsF6) have been studied by DSC and nuclear magnetic and electron spin resonance techniques. Measurements of the temperature dependence of Li-7 and H-1 relaxation times (T-1 and T-2) allow us to examine the greater motional freedom acquired by the Li+ ion and the chains in the hydrated complexes. Additional evidence for the increase of the lithium mobility is provided by the considerable reduction in the Li-7 NMR linewidth. Increase in hydration also increase the mobility of the free chains and may allow a volume expansion of the mobile segments, thus reducing the H-1 second moment. The ESR study performed on a copper salt-PEO complex reasserts that water competes favorably with the ethylene oxide unit for complexation with the positive ion.