The relative height (slenderness) of a tree, as the ratio of its height to diameter at breast height, is one of the most important characteristics of the morphological structure of a tree and a stand. At the beginning of the twentieth century, it was found that it is associated with species, the site quality, age and tree density. Numerous studies have shown that the relative height of a tree increases in direct relation to the degree of its depression in the canopy and is inversely proportional to the relative length of the crown. At the level of a stand, the relative height increases as the density of a stand increases and is described by a convex curve with access to the plateau. In practical application, relative height is used as an indicator of stability under wind and snow loads and as an indicator that affects the mechanical properties of the stem wood, and theoretically plays an important role in the theory of stem shape development. The purpose of our study was to perform a ranking of forest-forming genera (subgenera) of Eurasia by relative height. Based on the materials of 5858 model trees and 5175 stands for 11 tree genera (subgenera) growing on the territory of Eurasia, the influence of taxation indicators on the relative height of trees and stands of forest-forming genera, respectively, was established for the first time and their ranking by relative height was performed with fixed taxation indicators of trees and stands. All regression coefficients of the constructed models are significant at the level of p < 0.001, which ensures reproducibility of the results obtained. It is shown that the sequence of genera in the direction of decreasing the relative height of their trees and stands does not reflect the sequence of decreasing their light-requiring, by Ya. S. Medvedev (1910), in comparison with the available scales of light-requiring of European species.