This study was conducted in Fagus sylvatica-Quercus dalechampii stands in two areas in the Rhodope mountains of Xanthi. In order to analyse the structure and the development patterns of our stands, 23 plots were established, increment cores were taken, and stem analysis was conducted in 2 couples of dominant (competitive) beech and oak trees. The main results of this research indicate that a) In the mountainous part of the study area, natural and anthropogenic disturbances form the initiation, development and structure of beech-oak stands. However the fact that a number of oak trees survived after the disturbance in combination with landscape topography, which inhibited the dispersion of pine seeds, the species biology and the local climate, which is warmer than that of adjacent areas, influenced the succession pathways in the area and allowed oak to act as a pioneer species. b) Even though only one of the two structural types, tound in the submountainous part of the study area, was initiated by (anthropogenic) disturbances, the structure and composition of both structural types stands were and still are formed by illegal cuttings in which the oak wood is preferred. c) In both competing couples, the beech trees, after the first 80-85 years of their life, showed by far higher volume growth rates than the adjacent competitive oak trees which, in combination with the trees height growth patterns, implies, that in the future, a total domination of beech trees (in the two couples) will be observed. d) Forest practice must preserve the mixture of beech and oak in the mountainous part of the study area and enhance the presence of oak component in the submountainous part of the study area, in order to maintain· the diversity of these stands, to avoid the disadvantages of a homogenous forest and to mediate an orderly transition of community types, if the predicted increase in the average global temperatures comes true.