The effect of thermal pretreatment on the porous structure and adsorption properties of asphalt-based carbons activated with potassium hydroxide was investigated by FTIR, Raman spectroscopy, TEM, N 2 and CO 2 adsorption. Two series of the activated carbons were prepared by a one-stage method using KOH as the activating agent and a two-stage method including pretreatment of asphalt at 450 °C. A cross-effect of the KOH/asphalt ratio and pretreatment conditions on the characteristics of the porous structure of the activated carbons was revealed. The pretreatment of asphalt before activation is demonstrated to be a necessary stage for the effective control of the carbon porous structure by variation the KOH/asphalt ratio from 2 to 4. The porous carbon derived from petroleum asphalt exhibited the high CO 2 adsorption capacity of 3.8 mmol/g at 25 °C and 1 atm and good selectivity for CO 2 over N 2 , indicating possible applications in CO 2 capture technology. Graphical abstract