Ni(OH)(2)/multiwalled carbon nanotube (MWNT) nanocomposites were synthesized by in situ loading Ni(OH)(2) on the carbon nanotubes in an alkaline solution. The effects of the added carbon nanotubes on the morphology and electrochemical capacitance of Ni(OH)(2) were investigated in various loaded amounts of Ni(OH)(2). The MWNT substrates can reduce the aggregation of Ni(OH)(2) nanoparticles, inducing a good distribution of the nanosized Ni(OH)(2) particles on the cross-linked, netlike structure MWNTs. As a result, the rate capability and utilization of Ni(OH)(2) was greatly improved, and the composite electrode resistance was reduced. Under the optimal 70% mass load of Ni(OH)(2) in the composite, the capacity of the composite is 190 mAh/g at a current density of 0.4 A/g between 0 and 0.4 V vs SCE. The hybrid supercapacitor based on such Ni(OH)(2)/MWNT composite positive electrodes and activated carbon negative electrodes delivered a specific energy of 32 Wh/kg at a specific power of 1500 W/kg based on the total weight of the active electrode materials. It also exhibited good cycling performance and kept 90% of its initial capacity for over 2000 cycles.