To clarify the effect of shelterwood silvicultural method on the diversity of plant species in a beech (<I>Fagus orientalis</I>) forest in the north of Iran, we compared the plant species diversity in three compartments (treatments) where regeneration cuttings were performed with that in a primary compartment. The sampling procedure was a systematic random method and the tree, tree regeneration, shrub and herbaceous species were identified and measured within sampling plots. Results indicated that the mean tree richness in compartment No. 1 (only with one seed cutting) was higher than in the other compartments. The mean richness of understorey species in compartment No. 4 (with all regeneration cuttings) was higher than in the other compartments. The mean evenness (<I>E<sub>Var</sub></I>) of tree species in compartment No. 4 was higher than in the other compartments. The mean evenness of understorey species in compartment No. 1 was higher than in the other compartments. The mean tree diversities (i.e. 1-D, N<sub>2</sub>, H´ and N<sub>1</sub>) in compartment No. 1 were higher than in the other compartments. In addition, the mean diversities of understorey species in compartment No. 1 were higher than in the other compartments.