The present invention relates to innovative, nanoparticle-modified polyisocyanates, a process for their preparation and to their use in coating compositions and adhesives. The process comprises the steps of 1) reacting A) polyisocyanates with B) alkoxysilanes, and subsequently 2) incorporating by dispersion inorganic particles, optionally surface modified, having an average particle size of less than 200 nm as determined by means of dynamic light scattering in dispersion, where the alkoxysilanes are according to formula (I) Q-Z—SiXaY3-a  (I) in which Q is an isocyanate-reactive group, X is a hydrolysable group, Y is identical or different alkyl groups, Z is a C1-C12 alkylene group and a is an integer from 1 to 3.