Abstract: A combination of CO₂ activation and boiling in an alkaline solution was used to prepare highly mesoporous rice husk-based activated carbons. An orthogonal experimental design was used to investigate the effects of CO₂ flow rate, CO₂ activation time, NaOH concentration, boiling time and liquid/solid ratioon the porosity of the activated carbons. Results show that an activated carbon with a high mesopore volume of 79% can be obtained under optimized conditions with no need for high temperature treatment with NaOH. The specific surface area, pore volume and yield of the activated carbon can reach 899 m²·g^-1, 0.783 cm³·g^-1 and 26.2%, respectively.