Optical and structural characterization of ZnS thin films grown by chemical bath deposition (CBD), introducing for the First time a magnetic field (MF), are reported. Coming glass as well as Si and GaAs single crystals were used substrates, The effect of H-2-annealing, in the range of temperature 200-300 degreesC, and MF on the morphology and crystalline structure of films is studied in atomic force microscopy images and in X-ray diffractograms. MF does riot manifest appreciable influence on the grain size (GS) when glass substrates are used. On the contrary GS diminishes noticeably when MF is applied on ZnS/Si and ZnS/ GaAs CBD-growths. Further, an improvement of the optical properties with post-growth annealing in H-2, as exhibited by optical transmission, is obtained. An application of these ZnS films as antireflective coating is analyzed by reflectance spectra.