We compared the relationship of the behavior and performance of sugarcane baggase and rice straw as supercapacitor electrodes. X-ray diffraction revealed the evolution of crystallites of carbon and silica during activation at higher temperature. The morphology of the carbon samples was determined by SEM. The surface area, pore volume, and pore size distribution of carbon composites were measured. The electrochemical responses were studied by using cyclic voltammetry experiment at 25 ℃ in a three-electrode configuration. The specific capacitance of the sugarcane bagasse carbon electrodes was in the range 92-340 F/g, whereas for rice straw, it was found to be 56-112 F/g at scan rates of 2-3 mV/s. The sugarcane bagasse carbon exhibited better performance than rice straw carbon using H2SO4 as the electrolyte. However, the results clearly show that lignocellulosic wastes possess a new biomass source of carbonaceous materials for high-performance supercapacitors.