CO2 separation from flue gas with activated carbon (AC) as the adsorbent has received much attention and pressure swing adsorption (PSA) is considered to be a promising method for its application. Dynamic adsorption of CO2 simulates PSA operation and has been gradually adopted in laboratory study in recent years. The most important AC index determined in the studies is excess adsorption capacity of CO2, which is, however, prone to error frequently due to improper analysis of CO2 accumulated in the void spaces of the experimental setup and the packed pellets. The influence of N-2, the major component in flue gases, on CO2 adsorption was also not fully studied in the literature. This work presents a detailed study on these issues at the typical PSA conditions, CO2 pressures of 0.01-0.20 MPa and adsorption temperatures of 273.0-303.0 K. Results show that, in comparison to the excess adsorption capacity of CO2, the amounts of CO2 accumulated in the gap space between AC pellets and the pores space in AC pellets are usually small and can be neglected, but that in the system dead space is large and can not be neglected especially for small experimental setups. A general equation is proposed to determine the amount of CO2 in the system dead space at different operating conditions. N-2 has little influence on the excess adsorption capacity of CO2 under the conditions used in this work. (C) 2013 Elsevier B.V. All rights reserved.