This study is aiming at exploring the genuine role of CO2 in pyrolysis of lignocellulosic biomass by investigating the susceptibility of pyrolysis of monosaccharide (e.g., xylose and glucose), disaccharide (e.g., sucrose), and polysaccharide (e.g., woody biomass) to CO2. To do this, the thermal degradation of these four biomass samples was characterized in N-2 and CO2. The thermal characterization results reveal that the physical aspects of biomass decomposition (i.e., thermal degradation rate and residual mass difference) associated with CO2 were nearly the same; however, the chemical aspects were significantly different. In other words, CO2 enhanced thermal cracking of volatile organic compounds (VOCs) generated from thermal degradation of biomass. In addition, our experiment results show that xylose (a major constituent of hemicellulose) and lignin exhibited a high sensitivity to CO2 in pyrolysis. (C) 2017 Elsevier Ltd. All rights reserved.