This paper presents the results of the investigation into selective forest cutting using the FORKOME computer model. The verification of this model was achieved with field data from beech-dominated mixed forests (Dentario glandulosae-Fagetum) in Bieszczady, Poland. A selective felling was selected with chosen shade-generating trees for prognosis after the 1st, 15th and 25th years, and implemented into this model. A fast alteration in the biomass value and increased tree number was observed after cutting. These changes were due to increased light availability to the brushwood. The fifty year prognosis suggests that this tree stand composition will become increasingly multi-species and age-diverse.