Laser-induced NMR shifts are studied theoretically by semiclassical treatment as a dynamic Stark effect of optical fields. It is proved that light shifts in optical pumping experiment and in NMR and ESR spectra are based on the identical fundamental principle. The calculated NMR shift for a Hg-199 atom can be of the order of 1 MHz in a circularly polarized laser beam 10 W cm(-2) at a frequency near the singlet-triplet transition absorption.