The increased demand for high-quality multifunctional materials in the aeronautic industry requires the formulation and preparation of advanced nanostructured composites with superior characteristics. In particular, epoxy-based polymers, exhibiting excellent mechanical properties for structural stability, filled with carbon nanotubes (CNTs: single, double, and multiwalledSW, DW, and MW), characterized by remarkable mechanical and electrical properties, allow us to manufacture a very versatile class of composites for structural applications in automotive, aeronautics, industry, electronics, etc. Many aspects concerning the optimization of such composite systems are still to be clarified. In this paper, the physical properties of samples based on the epoxy resin with the same weight percentage (0.5%) of different CNTs have been studied. The physical behavior of the nanocomposites resulted to be dependent on the type and on the chemical functionalization of the nanoinclusions. The elastic modulus and the electrical conductivity of composites based on unfunctionalized CNT are higher than those obtained for the functionalized systems. Moreover, the maximum electrical conductivity achieved for the composite based on unfunctionalized MWCNT is not far from the target required for aeronautic applications. The contrasting results obtained for the different physical properties enlighten the difficulty in choosing one of the CNT types for the realization of multifunctional materials. (c) 2012 Wiley Periodicals, Inc. Adv Polym Techn 31: 205218, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21284