Residual trapping (also called capillary trapping), is expected to contribute significantly to CO2 storage capacity and long-term stability. However, it is believed to occur in water-wet rocks. As CO2 can decrease the water-wetness, the classical residual trapping can be compromised. On the other hand, adsorbed CO2 can serve as another type of residual trapping due to slow desorption rate. It has been observed that desorption of CO2 from a rock sample was hardly detectable, even after prolonged time under vacuum, indicating strong desorption hysteresis. The results suggest that in post-injection phase, a large part of adsorbed CO2 can remain immobilized. This will offset the decrease of capillary trapping and enhance solubility and mineral trapping.