The photocatalytic reduction of CO2 to carbon monoxide, methane and hydrogen (as a valuable byproduct) in the suspension or solution of various Zn-based forms in an alkaline environment and water, respectively, was investigated. These are the first results showing homogeneous CO2 photoreduction in the presence of Zn-based photocatalysts in an inorganic environment.The ZnO photocatalysts were suspended in the alkaline environment, while in water, they completely dissolved during at least 6 hours of carbonation, forming a transparent solution. The small crystallite size also determines a high zinc solubility in an aqueous solution (97.7 % for 14 nm, 92.2 % for 25 nm, and 68.5 % for crystallites larger than 100 nm). This homogeneous solution showed a slightly lower photoactivity than the heterogeneous suspension because of a lower concentration of crucial bicarbonate HCO3- ions. In both cases, the selectivity gives the order H2>CO>CH4. It was suggested that the photoactive centres in the dissolved agglomerates are the –Zn–O–Zn– hydrous bridges, which can use bicarbonate (HCO3-) ions as a transporter of CO2. In addition, the H+ ions generated during the ZnO dissolving in water can first participate in the CO2 photoreduction towards CO and CH4 and, afterwards, involve forming small quantities of hydrogen.