In the diploma we presented the development of forests on the level of departments in Idrija II forest management unit from the beginning of forest planning till today. We compared the data from plans for nine regulative periods from the year 1879 to 1998. With the analysis we monitored the development of the tree structure, stand structure and wood stock in the departments, and the growth development on the level of the entire department.In the beginning beech tree had predominated in the major area. By the middle of the century the share of the beech tree had regressed in the joint wood stock, and the share of fir tree, noble deciduous trees and pine tree had increased. The factor that influenced the changes of tree structures was large-surface felling, which was disadvantageous for the rejuvenation of fir tree and had an advantageous influence on the rejuvenation of beech tree and noble deciduous trees. The share of tree species in the joint wood stock was changing differently in separate parts of the unit. The share of pine treeincreased in mountain forests of beech tree and pine tree in the eastern part of the unit, the share of fir tree and noble deciduous trees increased inthe dinaric alder and beech tree forests, mountain and acidophilic beech tree forests in the western part of the unit. In the beginning of the period dealt with, the stand structure had been mostly single-measured, but in the recent years many-measured structure is predominating; the reason for this being gradual change of forest planning. In the first half of the century the oscillation of the wood stock amount had been greater due to the increased annual clearing and intensified felling just before the First World War, and in the second half of the monitored period due to the frequent sleet and wind breaking.