The scientific and industrial field of hybrid organic-inorganic polymer systems (HOIS) is widened in recent years due to possibility of combination of various organic and inorganic building blocks and obtaining hybrid materials with novel characteristics. The aim of the present paper is to develop the knowledge of the relationships between mechanical properties and structure of the synthesized HOIS. Novel hybrid organic-inorganic polymer systems have been synthesized by joint polymerization of organic and inorganic components due to reactions between their reactive groups, namely free NCO-groups in the organic component and OH-groups in the inorganic component. Creep and stress relaxation measurements of HOIS with different chemical composition of the organic component have been fulfilled. Good correlations between changes of mechanical parameters, structure of hybrid organic-inorganic networks, which are formed during synthesis of HOIS, and the theoretical model have been established.