The storage capacity of hydrogen in the tetrahydrothiophene and furan hydrates was investigated by means of pressure-volume-temperature measurement. The hydrogen-absorption rate of tetrahydrothiophene and furan hydrates is much larger than that of tetrahydrofuran hydrate in spite of same crystal structure (structure-II). The storage amount of hydrogen at 275.1 K is about 1.2 mol (hydrogen)/mol (tetrahydrothiophene or furan hydrate) (similar to 0.6mass%) at 41.5MPa, which is coincident with that of tetrahydrofuran hydrate. (C) 2009 Elsevier Ltd. All rights reserved.