Single tree parameters of a range of valuable broadleaved tree species were investigated in an 18-year old deciduous forest accrued from natural regeneration in Karnabrunn, located in the province of Lower Austria. Aiming at high valuable timber production in relatively short rotations this study was initiated to examine the releasing effects of different thinning intensities on the juvenile growth of a range of light demanding species such as sessile oak (Quercus petraea L.), common ash (Fraxinus excelsior L.), sycamore (Acer pseudoplatanus L.) and wild cherry (Prunus avium L.). The silvicultural prescription and objectives are applied in the following manner: Two geometrical thinning scenarios were established with a threshold distance around the selected trees of two meters in the first variant (V1) and three meters in the second variant (V2). In order to analyse the management effect, the single tree parameters of the selected elite trees sycamore and sessile oak were compared between the variants after the first tending operation taking place in the year 2004. Furthermore, the study was aiming to describe individually the competitive situation of the future crop trees in the two different thinning variants and to examine whether these indices of competition are reflected in the tree growth. Additionally, the correlation between important tree parameters such as crown width and length with the diameter was investigated. Within the given time frame of five years, no effect between the thinning variants could be stated on the single tree parameters dbh and height. Merely a difference of crown volume and the crown width/length ratio could be found. Nonetheless, the competition indices revealed a significant difference in all cases except Pretzschs index. The relation between diameter and crown width on the one hand and diameter and crown length on the other hand were significant. In conclusion, the naturally regenerated deciduous forest in Karnabrunn is managed for high valuable timber production and was ideal for examining the effect of thinning scenarios. The result show significant differences between thinning variants by competition indices, even though those were not strongly reflected in tree growth.