This work is undertaken by aerial laser scanning (LLS) and its use in forestry. The thesis describes a methodology for the derivation of some tree and plant sizes from LLS data. On 6 plots, the LLS identified the number of trees and their height with a spatial resolution of 0.5m, 1.0m, 1.5m, 2.0m, 2.5m, 3.0m. Areas 1-5 were found in mixed vegetation, and area 6 was represented only by deciduous woody plants, the stands were aged 65-150 years. On these areas, only some tree and planting quantities were surveyed and compared, ranging in size and height. Terrain measurement data were used as reference data for further calculations and comparisons. Using OPALS, the number of trees was identified, and the difference from the reference data ranged from 0% to 61%. Differences in height measured from LLS versus reference data ranged from less than 0.5% to 44% in one case.