The work presents the process of drying wood biomass after pre-treatment involving either debarking or crushing. The biomass used for research came from a robinia species wood. The material was dried in free-convection, at the drying medium temperatures of 40, 50, 60, 70 and 80 ◦C, respectively. Pre- treatment proved to have a significant impact on the drying rate, including the time required to reach moisture content of 10%, essential to start further treatment of biomass for power industry purposes. It was found that debarked samples of robinia lost water more quickly than the crushed ones. Samples that did not undergo pre-treatment took the longest time to dry.