Accurate estimation of carbon dioxide (CO2) sorption capacity of coal is important for planning the CO2 sequestration efforts. In this work, we investigated the sorption and swelling behavior of several Eastern and Western US coal samples from the Central Appalachian Basin and from the San Juan Basin. The CO2 sorption isotherms have been completed at 55 degrees C for wet and dry samples. The role of mineral components in coal, coal swelling, effects of temperature and moisture, and the error propagation have been analyzed. Changes in void volume due to dewatering and other factors such as caging of carbon dioxide molecules in coal matrix were identified among the main factors affecting accuracy of the carbon dioxide sorption isotherms. The (helium) void volume in the sample cells was measured before and after the sorption isotherm experiments and was used to build the volume-corrected data plots. Published by Elsevier B.V.