Polymer/carbon nanotube (CNT) nanocomposites have received much attention recently. In this study, we attempt to enhance the electrical conductivity of polyimide (PI) by variously modifying multiwall carbon nanotube (MWNT). We report the successful synthesis of PI/MWNT composite films using a blending process, and examine their properties and morphology. We modified MWNT by three different methods: thermal purification (U-CNT), oxidation with HNO3 (N-CNT) and modification with a silane coupling agent (G-CNT). We confirmed the successful preparation of the modified MWNTs by Fourier transform infrared (FTIR) and Raman spectroscopy, and transmission electron microscopy (TEM). The low amorphous surface characteristics of N-CNT produced low surface resistance in the range of 10(5)-10(6) O/cm(2) for the PI/N-CNT composites, which dispersed the buildup of electrostatic charge and improved dispersion. On the other hand, the better miscibility and interaction between G-CNT and PI, for the PI/G-CNT composites present superior thermal stability and mechanical properties. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012