The leaf area is one of the main quantitative indices of the size of photosynthetical apparatus of tree species. The total size of leaf area of tree crowns as well as its spatial distribution is specific for each taxon. Also the increase of leaf area during ontogenosis has a specific course according to tree species and conditions of environment. According to the dynamics and intensity of changes in increase of leaf area the author divides deciduous trees into 9 groups. Almost the half of the deciduous tree species growing in our country does not reach the leaf area of 500 m2. In the course of 50 years the largest leaf area has Aesculus hippocastanium L., large leaf area has Sophora japonica L., Acer saccharinum L., Robinia pseudoacacia L., etc. – they ought to form the base of town park composition. Quickly growing tree species reach during their short development only small or average leaf area. In the course of 50 years the majority of domestic species has only average or small leaf area.