Carbon nanotubes (CNTs) were modified by both chemical functionalization and mechanical shortening. The reaction kinetics of these CNTs-reinforced epoxy resins were examined according to the differential scanning calorimetry (DSC) characterization. It was found that kinetics parameters and reaction conversion were significantly influenced by the undertaken functionalization, and the magnitudes of influence were dependent on specific functionalization methodologies. Mechanical shortening of CNTs elevated the size effect-induced interference and diminished the reaction enthalpy and conversion. Chemical modification showed a double-edge effect on the reaction kinetics and the final effect was dependent on the balance of size effect-induced interference and participation of surface functional groups into reaction. Amino-grafted CNTs increased the activation energy of the curing reaction while epoxide-grafted CNTs slightly decreased the activation energy. These results will provide valuable guideline for the nanocomposites design, fabrication, and applications. (C) 2010 Elsevier B.V. All rights reserved.