This work investigates by means of molecular dynamics the filling of carbon nanotubes by carbon dioxide molecules. Nanotubes of various sizes are simulated and the resulting CO2 density calculated. The effects of various CO2 models are also investigated. The results show that the carbon dioxide molecules have a natural tendency to fill the nanotubes and the final CO2 concentration inside the nanotube can be approximately 100 times (depending on diameter and CO2 model) higher than that of the external atmosphere. (c) 2008 Elsevier B. V. All rights reserved.