CO2 adsorption onto two particle size classes of the commercial activated carbon Filtrasorb 400, namely 600-900 pm (sample F600-900) and 900-1200 mu m (sample F900-1200), was investigated at 293 K under model flue gas conditions in a fixed-bed column. Equilibrium adsorption capacity for a typical 15% CO2 postcombustion effluent was 0.7 mol kg(-1) for both investigated adsorbents. In both cases, CO2 breakthrough curves showed a reduction of the characteristic breakpoint time and faster capture kinetics at higher pollutant concentration in the feed (in the range 1-15%). Dynamic adsorption data highlighted the important role played by wider micropores in determining a quicker adsorption process for finer particles. Mathematical modeling of the 15% CO2 breakthrough curve allowed identifying intraparticle diffusion as the limiting step of the adsorption process. Numerical analysis provided values of the intraparticle mass-transfer resistances equal to 1.7 and 3.3 s for F600-900 and F900-1200, respectively.