The paper presents results of the research carried out in beech stands of the Carpathian beech fertile complex (Dentario glandulosae-Fagetum) in the lower subalpine zone in the Bieszczady National Park. The objective of the presented study was to analyse changes of species composition in all developmental stand of the lowers stands in the period from 1993 to 2003/04. The obtained results are proof of high levels of stability of the stands in focus, which was confirmed by absence, at the beginning and at the end of the control period, of statistically significant changes in species composition of the old trees layer, undergrowth and natural seeding. Enduringly, the Carpathian beech stands are build by three specific forest-forming species to the Eastern Carpathian Mts.: beech, fir and sycamore.