We tested two methods for measurement of the volume and surface of beech and pine tree crowns. The first method is based on an instrument called crown window, by means of which the volumes and surfaces of crowns were measured in sections, whereas the measurement according to the other method is based on geometric shapes. The sample comprised 60 beech and 40 spurce trees. The measurements of the volume and surface on the basis of geometric shapes were compared with the measurements made by the sections of the tree. We found major discrepancies in the measurements, especially with the upper, sun-exposed part of the beech tree crown, which is illustrated by a cubical paraboloid. The measurements tally to a greater extent with the pine tree. We assumed that the indicators of the shape of the crown that were used would change with the thickness of the tree; however, this is only true of certain indicators. When establishing the interdependence of the increment and the crown parameters, we realized that with the beech tree the upper, sun-exposed crown more strongly influences the increment than the lower, shady part of thecrown, whereas it is just the opposite with the spurce tree. We also compared the actual heights of the trees with the heights measured with the crown window and height meter Suunto and we found out that the differencies gets bigger with the growing height of the tree; the mistake also depends on the microrelief.