Abstract: Nanocarbon/polyaniline (PANI) composites were prepared by in situ polymerization of aniline on carbon blacks (CB), carbon nanotubes (CNTs) and graphene nanosheets (GNSs). The GNS/PANI composite has the highest PANI content with high specific capacitance, low internal resistance as well as improved cycling stability and rate capability. Of the three, the GNS/PANI composite shows better performance than CB/PANI and CNT/PANI. This can be attributed to the following three characteristics of GNSs as the PANI support: (a) the two-dimensional planar structure is beneficial to homogeneous nucleation of a large amount of PANI on their surface, giving more active sites for the redox reaction; (b) the planar contact between GNSs and PANI is good for constructing a conductive network with a high electron transfer rate and a low resistance and (c) the layer-by-layer stacks of crumpled GNSs and PANI layers prevent the peeling of PANI from the graphene surface. As a consequence the material can tolerate severe volume changes, swelling and shrinkage of PANI, during charge/discharge.