In this work, stem wood and branches and tops of Norwegian spruce and birch were carbonized at different pressures, producing charcoals of which the CO2 gasification reactivity was studied by means of a thermogravimetric analyzer operated isothermally at 850 °C. The results reveal that the gasification reaction rates of charcoals produced under higher pressures was lower than those produced at the atmospheric pressure. Clear correlations between the CO2 gasification reactivity of the charcoals and their fuel and chemical properties, including the catalytic effect of the inorganic matter, were observed. The semi-empirical power law kinetic model described well the gasification behavior with high fit quality. The activation energy was found to be within 140–160 kJ/mol, whereas the reaction order varied in the range of 0.4–0.6.