Composites based on carbon nanostructures (CNS) and poly(epsilon-caprolactone) (PCL) were produced by solvent casting technique. Single-walled carbon nanotubes (SWCNTs) and carbon nanofibers (CNFs) were selected, to produce composite films with enhanced properties. The role of CNS type and percentage were investigated in terms of morphological, thermal, mechanical, and dielectrical properties. Composite morphological analysis reveals a good dispersion of CNS, at low and high content. Thermal properties underline the nucleation effect of CNS on PCL polymer matrix. Reinforcing effects in terms of increased tensile modulus were obtained with both nanofillers, but a higher reduction of the ductility was shown in PCL/CNF materials. A higher efficiency to form a conductive network, assessed by AC conductivity, was observed for SWCNTs at concentration lower than 1 wt. % (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3544-3552, 2011