A number of 3,1-benzoxazin-4-ones and 4(3H)-quinazollnones and their thiono analogues were recorded with high resolution1H NMR 400 MHz spectrometer. The magnetic anisotropic effect of (C˭O) and (C˭S) groups was also discussed. The study of1H NMR chemical shift correlated to 2-D PHR allowed the complete assignment of such structure. The introduction of sulphur atom has influenced remarkably the chemical shift of H5of the benzeniod moiety as well as the chemical shift of the two ortho protons of the phenyl group.