A series of epoxy nanostructured coatings based on diglycidyl ether of bisphenol A (DGEBA) and an isophorone diamine crosslinker was prepared. Top-down nanocomposites (3% nanofiller) were obtained by the mechanical dispersion of nanoalumina, silanized nanoalumina, and organomodified clays. Bottom-up hybrids were instead achieved after the silanization of the DGEBA resin and after cocrosslinking with tetraethylorthosilicate through a self-catalyzed sol gel process. The curing process of the nanocomposites was studied by differential scanning calorimetry and suggested an overall increase in the crosslinking kinetics in the presence of nanoparticles. Other characterization included dynamic mechanical analysis, Buchholtz indentation hardness testing, and Taber abrasion testing. Finally, atomic force microscopy (AFM) techniques were used to study the surface morphology of the coatings and to produce nanoscratches. We concluded that, in the top-down nanocomposites, there were minor changes in the surface hardness and a slight improvement in the abrasion resistance, whereas the nanoscratch resistance assessed by AFM tests showed significantly better performances in the hybrid coatings obtained through sol gel chemistry. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1720-1727, 2010