[en] Polyimide nanocomposites prepared by the in situ generation of crosslinked organosilicon nanophase by sol-gel techniques were investigated by dielectric relaxation spectroscopy, themally stimulated depolarization currents and dynamic mechanical analysis. Two series of samples were investigated with molar mass 5000 and 10000 of the polyimide chains. In both series a non-additive decrease of the dielectric permittivity with increasing amount of filler was observed, indicating a loose inner structure of the spatial aggregates of the organosilicon nanophase. The magnitude of the dielectric γ relaxation of polyimide was found to increase with increasing filler content for the shorter chains, whereas the opposite was observed for the longer ones