Two types of the polymer organic-inorganic nanocomposites have been prepared and studied.The epoxy based organic matrix was reinforced with (a) in situ generated silica nanostructures or with (b) well defined inorganic nanobuilding blocks polyhedral oligomeric silsesquioxanes (POSS).Generally, the nanocomposite properties are mainly determined by morphology of the hybrid system and an interface interaction.Our goal was to control the hierarchical structure of the polymer nanocomposites from the molecular up to macroscopic level by modifying an interaction between phases.