xLiF . (1-x)LiPO3 glasses with x = 0; 0.30 and 0.35 were studied by Li-7, Li-6 and F-19 nuclear magnetic resonance (NMR). At high temperatures, the Li spin-lattice relaxation is dominated by dipolar magnetic fluctuations while at lower temperatures electric field gradient fluctuations cause the relaxation. From these studies, and supported by investigations of the F spectrum, we conclude that, in LiF doped samples, two types of regions ("clusters") exist which are structurally different. Li linewidth data suggest that the increase of conductivity in LiF doped samples, compared with undoped samples, is due to the larger number of charge carriers rather than to an increase of lithium ion mobility.