Site occupation and structural change in Li substituted AgNbO3 were probed by Li-7 NMR. Characteristic changes in the Li-7 NMR spectra depending on Li content were observed. Analysis of integrated intensity of the spectra revealed that 16% of substituted Li+ ions occupy quasi-stable sites induced in crystal structure at 300 Kin the 5 mol% Li substituted sample and would be in the state of motion, which are comparable to that of Li+ ion in LiNbO3 at high temperature. On the other hand, it was found that the Li+/Ag+ sublattice in the 12.5 mol% Li substituted sample is easily made unstable by structural disturbance introduced in structure and the instability of the sublattice stimulates a local Li+ ion motion via quasi-stable sites at room temperature. An appearance of the quasi-stable sites in local structure due to the Li substitution is closely related to instability of the Li/Ag sublattice and Li+ ion dynamics in Li substituted AgNbO3. (C) 2013 Elsevier B.V. All rights reserved.