The one-dimensional 1×1 and 1×2 tunnel structures of manganese dioxides, pyrolusit(β-MnO2) and ramsdellite (R-MnO2), respectively, were chemically intercalated with LiI. Two 7Li resonances were observed in lithiated pyrolusite. One isotropic resonance arising at 110 ppm shows a short spin-lattice relaxation time (T1 ∼ 3 ms) and was assigned to Li+ ions in the 1×1 tunnel structure. The other isotropic resonance arising at 4 ppm shows a long spin-lattice relaxation time (T1 ∼ 100 ms) and was assigned to Li+ ions in diamagnetic local environments in the form of impurities such as Li2O or on the surface of the MnO2 particles. Three 7Li resonances were observed in lithiated ramsdellite at very different frequencies (600, 110 and 0 ppm). The resonance at 600 ppm, which is observed at low lithium intercalation levels, is assigned toLi+ ions coordinated to both Mn(III) and Mn(IV) ions in the 1×2 tunnels, while the resonanceat 110 ppm is due to Li+ ions coordinated to Mn(III) ions and appears at higher Li levels. The resonance at 0 ppm is associated with a long spin-lattice relaxation time (T1 ∼ 100 ms) and is also assignedto Li+ ions in diamagnetic impurities.