Li-7 NMR spectra, spin-lattice and spin-spin relaxation times have been measured at various temperatures between about 100 K and 800 K at frequencies of 16 MHz and 117 MHz for two novel crystalline lithium boron sulphides with high ionic conductivity. The thioborate network of the ternary compound Li9B19S33 possesses a large number of extended channels, the quaternary compound Li4-2xSr2+xB10S19 (x approximate to 0.27) is distinguished by a layered structure leaving cavities and channels in between. Both structures provide an extended sublattice of partially unoccupied lithium sites. The complex behaviour of spectra evolution and relaxation is similar to that in other crystalline and glassy thioborates and can be explained in terms of the anisotropic diffusion through the channels. The activation energies of the principal processes are 22 kJ mol(-1) and 47 kJ mol(-1), respectively, for the two materials. Most striking is the appearance of well-resolved quadrupole spectra at elevated temperatures which may be considered as a line narrowing average of the broad spectral distribution at low temperatures. The spin-lattice relaxation rates display Kohlrausch-Williams-Watts behaviour; it may as well be described by an asymmetric distribution of correlation times or a modified BPP equation.