The thesis deals with the evaluation of reliability of data about forest stands on the basis of control sampling method in the Semič Forest Management Unit. On the basis of data from permanent sampling plots, which have been measured in 1995 and 2005, we estimated how reliable the measurements on sampling plots were and above all which tree species have been subject to separate changes. We also evaluated which data and information about structureof the stands and their diversity is possible to be acquired on the basis of control sampling method. We calculated the estimation about stand structure and species diversity of the stands for individual strata and then we compared our estimations with the data from the forest management plan. This comparison revealed differences, which are also the result of different ways of gaining data. If we have sufficient number of sampling plots with regard to individual strata the control sampling method is suitable for observing the development of forests and evaluating standsć parameters.