In this article we present an application of the IBP index (Potential Biodiversity Index), used for assessing potential biodiversity in forest stands. The proposed index is based on the score of ten factors: seven are related to forest management (structural particularities of the forest) and three are related to environmental context. The study was conducted in a mixed forest located in Ursoaia area from Frasin, Suceava Forest Department, Romania. The factors were evaluated in 96 plots from 6 forest stands, 3 of them included in a scientific reservation, and 3 are timber production stands. The index values were calculated for each plot, and further for each forest stand. Index values varied from a stand to another, also within the same stand, from one sample plot to another according to the specific feature identified in each plot. The index values were higher in the stands included in the scientific reservation. This is explained by the number of tree species, the high number of large trees, the vertical structure of the stands, the amount of dead wood. IBP – index is a good tool to evaluate the forest biodiversity. The results can be analyzed for longer periods of time, and also may indicate the factors that can be improved by specific actions