The elastic, dielectric and thermodynamic properties of zinc blende ZnS and ZnO are comparatively studied using first-principles ground-state and response-function calculations. Our results show that the two phases have similar dielectric properties. ZnO has a larger bulk modulus, but it becomes soft more quickly than ZnS as temperature raises. The linear expansion coefficient of ZnS is several times larger than ZnO at room temperature. The reasons for the differences in physics properties are explained from the features in atomic combination of the two phases. (c) 2005 Elsevier B.V. All rights reserved.