Solid-state C-13 NMR spectra and ab initio calculations of C-13 NMR chemical shifts show that poly(ethylene oxide) (PEO) carbons in complex with LiCF3SO3 (both in crystalline and amorphous phase) are more shielded in comparison with neat PEG, due to the coordination to the Li+ cation. The results obtained from C-13 NMR cross-polarization dynamics are in agreement with the published X-ray crystal structure of the PEO/LiCF3SO3 complex. The mobility of PEO in the crystalline complex is lower than in neat crystalline PEO.