We have carried out a project to clarify the active site and the role of ZnO in Cu/ZnO-based catalysts for methanol synthesis from CO2 and H-2 using both classical catalytic and surface science techniques. The active site model in which Zn species present on the Cu surface promote the methanol synthesis had been initially proposed based on the results of the powder catalysts such as a physical mixture of Cu/SiO2 and ZnO/SiO2. The promotion of Zn has then been proved by a model catalyst of a Zn-deposited Cu(1 1 1) surface. The mechanism and kinetics of the methanol synthesis over Zn/Cu(1 1 1) as well as the structure of the active site have been studied on the atomic level by surface science techniques, such as XPS, AES, LEED, IRAS, and STM. A metallic Cu-Zn surface alloy is a catalytically active species for the methanol synthesis from CO2 and H-2.