Due to increasing demand for forest products, fast-growing species such as poplars are grown in plantations to a larger extent. The quality of wood raw material depends to a greater extent on its physical properties. The available data on physical and mechanical properties of white poplar wood grown in Republic of Croatia and Serbia are insufficient. In this article, preliminary results on physical properties of white poplar clone 'L-12' wood grown in Republic of Croatia and Serbia are presented. Five representative trees of white poplar clone 'L-12’ from two sites were collected. One is located near the city of Osijek in the Republic of Croatia, within Osijek Podravina forests and the other one is located at Experimental Estate of the Institute of Lowland Forestry and Environment “Kaćka šuma” near the city of Novi Sad in the Republic of Serbia. Both sites are representatives of breeding poplar plantations. The investigations were carried out using only segments with north and south orientation in wood at the breast height of each tree. The results of average values indicate that there is no significant difference in wood density in clone 'L-12' between two sites. There is significant difference in longitudinal, tangential and volume shrinkage and maximal moisture content between sites, but the difference, as far as practice is concerned, is negligible. For a better prediction