Carbon aerogels have been prepared through a polycondensation of cresol (Cm) with formaldehyde (F) and an ambient pressure drying followed by carbonization at 900°C. Modification of the porous structures of the carbon aerogel can be achieved by CO2 activation at various temperatures (800, 850, 900°C) for 1–3h. This process could be considered as an alternative economic route to the classic RF gels synthesis. The obtained carbon aerogels have been attempted as electrode materials in electric double-layer capacitors. The relevant electrochemical behaviors were characterized by constant current charge–discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy in an electrolyte of 30% KOH aqueous solution. The results indicate that a mass specific capacitance of up to 78Fg−1 for the non-activated aerogel can be obtained at current density 1mAcm−2. CO2 activation can effectively improve the specific capacitance of the carbon aerogel. After CO2 activation performed at 900°C for 2h, the specific capacitance increases to 146Fg−1 at the same current. Only a slight decrease in capacitance, from 146 to 131Fg−1, was observed when the current density increases from 1 to 20mAcm−2, indicating a stable electrochemical property of carbon aerogel electrodes in 30% KOH aqueous electrolyte with various currents.