The paper is devoted to the analysis of suspended solids influence on water transparency in freshwater lakes of Altai Krai during 2014–2015. The data on the quantitative composition of polydisperse suspension particles and the size distribution are presented, and the spectral contribution of lake water components to the light attenuation coefficient is estimated. The greatest contribution of suspension to the total attenuation coefficient ε at λ = 430 nm (winter) was found in Lake Krasilovskoye (more than 70 %) and in Lake Bol’shoye Ostrovnoye (80.5 %) in springtime. Yellow substance makes the largest contribution to the attenuation coefficient ε (in winter) in Lake Krasilovskoye; at λ = 430 nm it makes up 81.9 %. Clean water makes a negligible contribution to the light attenuation (λ = 430 nm) in all waters and does not exceed 0.1 %, increasing sharply in the long-wave region (17 % in Lake Lapa, and 29.5 % in Lake Krasilovskoye at λ = 670 nm). Maximum contribution of chlorophyll to ε is observed in winter only in Lake Bol’shoye Ostrovnoye (10.4 %); that is by an order greater than in Lake Lapa (0.5 %). In spring and summer periods it is the largest in Lake Krasilovskoye — 36.5 % and 35.1 %, respectively, at λ = 430 nm. Molecular light scattering by clean water in the spectral range under study does not contribute significantly and is less than 0.1 %. The study of optical properties of the surface layer of the lakes shows the highest light attenuation in Lake Bol’shoye Ostrovnoye as compared to the other lakes. This is due primarily to a high content of suspension and yellow substance, and water temperature fluctuations, and consequently, the change of chlorophyll concentration in phytoplankton of lakes.