The present paper describes experiments to explain a residual improvement of the adhesion after chemical blocking of the surface oxides in composites with HT-fibers. For this purpose, a carbon fiber was selected which does not show any difference in surface neither between non-surface treated and surface treated states nor after desorption treatment of the surface treated fibers. It seems probable that the residual nitrogen content in HT-fibers causes the residual adhesion in the range of 60 MPa to 80 MPa in carbon fiber reinforced plastics (CFRPs).