The purpose of the porosity measurements was to compare the boards made by two different methods: the conventional, hydration curing method and the CO₂ injection method, and to find out how their porosity affects water absorption. The specific pore-surface area of the CO₂-hardened boards was much smaller than that of the hydrated cement-bonded particleboards. Regarding the pore size distribution diagram, in the case of the CO₂-hardened boards, there were two peaks on the graph (one peak at a pore diameter of around 6-8 µm, and a second peak at around 2 µm), and in the case of the conventional boards there was only one peak at 2 µm. The total pore volume of the CO₂-hardened boards was larger than that of the hydrated boards. Water absorption of the CO₂-hardened boards was lower than that of the hydrated particleboards. There was no relationship between the specific pore-surface area and water absorption, and between the total pore volume and water absorption. The use of CO₂ did not affect water absorption and these boards still displayed a higher initial strength.