The main topic of this displome thesis is the examination of ancient trees of privat green arear in the Mödling city/Lower Austria worth being preserved by means of a special register considering the age of the trees. The empiric part was done in close co-operation with the municipal council of the city of Mödling and under support of the daily paper "Niederösterreichische Nachrichten". 69 preserve worthly trees have been selected in the area of Mödling and examined according to the creterions of register. Analysing the data we obtained clear results clear results concerning the significance of ancient trees in privat green areas for townscape and microclima. As well, the relevance of tree cut for the physiological and morphological conditions of the trees. The empiric investigations and evaluations further resulted in possibilities of long-term preservations of ancient trees and the choice of necessary measures.