We studied mechanochemical modification of low-dispersed SnO 2 and high-dispersed SnO(OH) 2 powders with specific surface area 6 and 198 m 2 /g. They are perspective materials for photocatalysis and adsorption. The aims of work were: the study of crystal, porous, and electronic structure of obtained products, evaluation of their photocatalytic activity under visible light in the process of dyes degradation. The mechanochemical treatment of powders carried out in air and water at 300-850 rpm using a planetary ball mill Pulverisette-7 (German, «Fritsch»). We used XRD and DTA-TG analysis, UV-Vis and FTIR spectroscopy, adsorption-desorption of nitrogen for characterization of initial and modified samples. We have established that porous structures of investigated samples of powders are changed under milling. The initial high-dispersed powder is porous and poorly crystalline. Its specific surface area decreases after milling: from 198 m 2 /g for initial sample to 130 and 187 m 2 /g for samples milled in air and water at 850 rpm, respectively. On the contrary, low-dispersed powder is almost non-porous and well crystallized. Its specific surface area increases about 2 times, but the degree of crystallinity reduces as a result of milling. In general, milling of both powders in water leads to formation of meso-macroporous structure. The shift of band gap and increase in adsorption of visible light occurs after modification of high-dispersed sample. This may be a result of changes in the phase and chemical composition, the size of the crystallites, the degree of hydroxylation of the surface, as well as the formation of defects in the structure. On the other hand, the narrowing of band gap occurs after mechanochemical treatment of low-dispersed sample. As a result, photocatalytic activity in the process of rhodamine B degradation under the action of visible light for all modified powders significantly increases. Maximal activity showed high-dispersed sample milled in air and water at 850 rpm. The degradation rate constants Kd are 7.3•10 -5 and 6.4•10 -5 s -1 , respectively. The results of the measurement of total organic carbon content in solution after degradation indicate that not only the discoloration of the solution occurs, but also the partial mineralization of the rhodamine. Thus, the degree of mineralization is up to 75 %.