This study deals with the characteristics of wood of two different species of oaks, the non-native northern red oak (Quercus rubra L.) and the native pedunculate oak (Quercus robur L.), growing in a reclaimed surface brown coal mine in the Czech Republic. The differences in the wood density of the aforementioned species, including the impact of position in the trunk, were examined. The impact of annual ring width and the proportion of latewood on density were also evaluated. The density of Q. robur wood reached 707 kg·m-3, which was significantly higher than that of the North American species, which reached 654 kg·m-3. Moreover, in the radial direction, the density increased in the direction from the pith toward the bark for both Q. rubra, and Q. robur. In the vertical direction, the density reached its highest value at the basal part of the trunk, but statistically, this assertion was only significant for Q. rubra. The effects of annual ring width and the proportion of latewood on density were shown to be statistically very low for both oak species.