Cadmium sulfide photocatalysts for H-2 production from water using visible light were prepared by different techniques, i.e., liquid-liquid, gas-liquid, and solid-liquid reactions. The crystallite size and distribution, band gap, and stoichiometric composition of cadmium sulfide and consequently the activity were affected by the preparation technique. The activity of cadmium sulfide showed a strong correlation with its semiconducting (n- or p-type) behavior. Cadmium sulfide that was prepared by gas-solid reaction had excess interstitial cadmium ions in the lattice, which had been attributed to its n-type semiconductor behavior and superior activity. The n-type behavior of cadmium sulfide has been correlated to its stoichiometry.