Dissociative adsorption of H₂ on ZnO, apart from the bands due to OH and ZnH stretching vibrations, gives rise to bands at ca. 840 and 810 cm^-1 which can be attributed to the bending modes of these surface structures. Analysis of the integrated intensities of the bands arising after H₂ and HD adsorption at 100 and 300 K shows that both the 840 and 810 cm^-1 bands are due to ZnOH group vibrations. Their shift after ¹⁸O isotope substitution of surface oxygen, only 1 and 2 cm ^-1, respectively, implies that they cannot be associated with the Zn-O vibration or its overtone enhanced by Fermi resonance. They should be attributed to two bending modes of surface hydroxyls. After HD and D₂ adsorption a band for the OD bending vibration was detected at 637 cm ^-1. In accordance with these data, ν_OH(D) + δ_OH(D) combinations were observed at 4297 and 3195 cm ^-1, which give the values of 807 and 611 cm^-1 for δ_OH and δ_OD, corresponding, apparently, to the more intense low-frequency component.