We describe the fabrication of nanocomposites and study their electrical properties using two different types of polymers: polystyrene (PS) and poly(butadiene-co-styrene) (PSBS), in conjunction with N-doped multi-walled carbon nanotubes (CNx MWNTs). The N-doped tubes were embedded in the polymer matrix in two ways: as produced and PS-grafted using an atomic transfer radical polymerization (ATRP). We found that the grafted tube composites displayed higher percolation thresholds when compared to ungrafted tubes: from 0.45 vol.% for ungrafted to 1 vol.% for PS-grafted tubes in PS matrices, and from 1 vol.% for ungrafted tubes to almost 2.5 vol.% for PS-grafted tubes in PSBS matrices. The results demonstrate that PS coated tubes result in more efficient dispersions but exhibit higher percolation thresholds, whereas pristine doped-tubes result in better electrical conducting nanocomposites. (c) 2007 Published by Elsevier B.V.