This work presents the non-Darcy behavior results of CO2 compared to the previous work using N2. This work is based on 85 series of high-velocity gas flooding experiments under high-pressure and high-temperature. Based on experimental results, it was found that pore pressure has more influence on permeability in CO2 flooding than that in N2 flooding. In contrast, temperature has definite and consistent influence on both permeability and non-Darcy flow coefficient in N2 flooding, but the same influence in CO2 flooding was not observed. Mechanism behind these differences is attributed to physical property differences of the two gases. Much of the work was near the CO2 critical point or liquid regions. Other anomalies are attributed to thermal effects caused by expansion cooling of the CO2. Field data indicates that this phenomenon could be responsible for productivity loses in high CO2 wells. Accordingly, attention should be paid to avoid flowing CO2 at conditions near its critical point.