Hybrid nanocomposite membrane films with different silicon contents (4.5-12.3%) are acquired by the hydrolytic polycondensation of tetraethoxysilan (TEOS) in 4% solution of cellulose diacetate (CDA) and ethylcellulose (ECel) in organic solvents (acetone and tetrahydrofuran (THF)). Fourier IR spectroscopy is used to confirm the formation of a Si-network with Si-O-Si bonds that are linked with the cellulose derivatives by H-bonds. Hybrid films are insoluble in aqueous solutions containing 5-20 vol % of an organic component. Atomic force microscopy is used to confirm the presence of nanosized structures on the surfaces of the obtained films. The sizes of these structures depend on the polymer nature ratio of polymer and TEOS in synthesis, and they reduce as the Si content in the film increases. The equilibrium degree of swelling of hybrid films and a coefficient of diffusion of an organic substance from organic-water solutions (acetone water or THF water) are highest for the films obtained at the equimolar ratio polymer-TEOS in synthesis. The thermodynamic parameters of the interaction between hybrid films (Flory-Huggins parameter) with the liquid medium, as well as the factor of the relation THF from the THF-water solutions in Ecel/TEOS films, are calculated. Correlations of the structure and composition of hybrid films and their behavior in organic-water solutions are shown and discussed.