AbstractWe report investigation of electrical conductivity of high resistivity polystyrene/carbon nanotube composites. The films consisted of a thiol‐bonded network of wrapped MWNTs within a polystyrene matrix with mass ratios ranging from 0% to 1%. The electrical conductivity and its thermal activation energy were systematically depending on the CNT doping level. A number of phenomena could be explained by the presence of CNT ‘islands’ in the polystyrene matrix at doping levels below the percolation threshold. At higher levels of CNTs an interconnected conducting network is formed. The results appear consistent with fluctuation‐assisted tunnelling through barriers between conducting carbon nanotubes for medium and large voltages. However, at low voltages there is a sharper decrease in conductance as voltage decreases that could arise from Coulomb blockade effects or other small barriers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)