Silanes are silicon based compounds which can react with inorganic and organic substrates or between themselves. By the reactions of hydrolysis and condensation silanes are binding to inorganic substrates, while by the reactions of endcapping, radical grafting and copolymerisation silanes are binding to organic substrates. Silane coupling agents are organosilanes which are capable of creating strong chemical bond between organic and inorganic materials. They are being used because they enhance the chemical resistance of the bond across the interface. Their application is: surface modification, adhesion promotion, as dispersing/hydrophobing agent, crosslinking agent and many more. The most important application for this thesis was modification of hydrophilic and hydrophobic properties of surfaces. Hydrophilicity and hydrophobicity are determined by measuring the contact angle of water droplets on the substrate surface. If the contact angle (θ) is greater than 90° the surface is hydrophobic, but if it is smaller than 90° the surface is hydrophilic. This thesis examined the influence of silanes on on the surface properties of selected polymers. While conducting experiments the main aim was to bind a thin layer of silane on the surface of polymer, which would make the surface hydrophobic. Samples of polymers PE-HD, PE-LD, PLA and ABS were dipped in silane solutions of different concentrations. Silanes used were Dynasilan DAMO, SIVO 160, SIVO 214 and 6490 from Evonik, 1H,1H,2H,2H-perfluorooctyldimethylchlorosilane from abcr GmbH (PFODMCS), Erdal Water Stop from Werner & Mertz, Bama Power Protector from S.C. Johnson Bama GmbH, Rain-X Rain Repellent from Rain-X and Anti Aqua from Steuber GmbH. Prepared samples were investigated using the contact angle method in order to determine if the surface is hydrophobic or hydrophilic. FTIR-ATR analysis was implemented to determine changes in chemical composition of polymer surface. The contact angle method results showed that the surface of certain samples became hydrophobic by applying some of the silanes on them. FTIR-ATR analysis shows that Si-O-Si bonds were formed on the surface of polymer. Furthermore, if the higher concentration of silanes is used, then thicker layer is formed on the surface, which causes amplification of the absorption band's intensity.