The assessment for realistic CO2-adsorption capacities of different rocks is important for understanding the processes associated with CO2 storage. This paper investigates the adsorption characteristics of rocks for CO2 (limestone, sandstone, marl, claystone, clay, siltstone and metamorphic rock) by using a gravimetric method. The measurements were performed at 21°C with pressures from 1 up to 4 MPa. Sandstone (and clay with sand/sandstone) showed the largest adsorption capacity at 21°C. The highest amount of in situ CO2 contents in measured samples was 21.4 kg/t. The CO2-adsorption capacities were lower than past results in different coal samples. The results indicate that adsorption of CO2 into rocks may play an important role in storing CO2 in subsurface rock. Copyright © 2012 John Wiley & Sons, Ltd.