The effect of coal rank on hydrogen generation during the reaction of coal/CaO and char/CaO mixtures with high-pressure steam was investigated using a flow-type reactor, and the results were compared with the results for the gasification of the same coal and char sample in the absence of CaO. For the coal/CaO mixture, reactions of coal, CaO and CO with steam, and CO2 absorption by CaO occurred simultaneously in the reactor and H-2 was the primary gas product. CO2 was fixed by CaCO3, and CO was completely converted to H-2. The rates of H-2 generation per mole of carbon in the coal (char) samples decreased in the order of lignite > sub-bituminous > bituminous. The rate of H-2 generation seemed to be affected by both the reactivity and the carbon content of the coal.