Analysis of the branch area/stem area ratio of Scots pine growing in different climatic conditions in Europe and Siberia indicates that the branch area supported by a stem increases in warmer and drier conditions. The ratio was significantly correlated with several climatic variables, especially with potential evapotranspiration (E p). The ratio was negatively correlated with stand density (d s). A regression model combining E p and d s accounted for 85% of the total variation. These trends are believed to reflect hydraulic segmentation of trees and may represent a strategy to avoid cavitation in the tree, especially in the branches.