In 2010, in the part of section 13 of the forest management unit Trnovo a thinning was performed with mechanized harvest technology in pure beech polewood stands, while in the other part of this section with similar forest stands, the thinning has not been made. We found significant differences between thinning and no thinning part of section in stand basal area, quadratic mean diameter and volume. No significant difference was found for number of trees and Reineke's stand density index. Analysis of spatial tree distribution has shown that thinnings create more homogenous spatial patterns of trees in stands. We delineated the gaps before (year 2006) and after (year 2010) thinning. Gap dynamics has shown that intensity of forest management influence the area and number of gaps. The spatial proportion of gaps decreased from 1,3 % to 1,1 % in the part of section without thinning and increased from 0,41 % to 10,7 % after thinnings. In the both periods small gaps (<200 m2) prevailed with 90 % and 86 %, respectively. In the section 30 with unevenaged stands we delineated the gaps with lidar data. Gap delineation on different hights of trees and other vegetation in year 2011 has shown, that in unevenaged stands prevailed gaps of different tree hights. The proportion of gap area in this section has increased from 5,6 % in 2011 to 18,5 % in 2013.