In the decision making process concerning numerous objects researchers frequently face the problem of selecting an appropriate method to link them into groups of similar objects. This study is a proposal of the application of agglomeration methods to search for relationships between individual forest ecosystems in terms of their water retaining capacity. It was assumed that most parameters describing water retaining capacity of a specific ecosystem should come from forest management plans. Selected characteristics, adopted as those describing water retaining capacity of forest ecosystems, i.e. mean fall of land [%]; distance from watercourse network [m]; distance from standing waters, wetlands (lakes, ponds, swamps) [m]; site moisture content variant [-]; stand density index [-]; type of soil cover [-]; undergrowth cover index of the experimental plot [-]; canopy index [ha∙ha-1] and potential available water retentiveness of the soil profile [mm] were tested using seven data clustering methods, i.e. the single linkage method, group average method (UPGMA – Unweighted Pair-Group method using arithmetic averages), weighted average method (WPGMA – Weighted Pair-Group Method using arithmetic Averages), the furthest neighbor method, the unweighted centroid method (UPGMC – Unweighted 169 Pair-Group Method using Centroids), weighted centroid method (WPGMC – Weighted Pair-Group Method using Centroids) and ...