In forests whose main purpose is conservation and service production, it is not possible to accurately reflect the potential production of the planning unit if the planning is made only based on actual structure and the utilization is based on this without the calculation of the optimal structure. This approach does not comply with the principle of efficiency. The aim of this manuscript is to carry out how the optimal structures of erosion prevention and hydrological functions can be determined in forests managed by protection purposes. Odayeri Planning Unit was selected as the study area and the optimal structures have been determined by taking into account the forest inventory data, yield tables and criteria determined for forest functions. In the soil protection working groups, the optimal structure was determined according to the French Volume Method by taking into account the parameters of target volume, rotation length, target diameter and continuous forest form. In the water conservation working groups, the optimal structure was determined with the evenaged forest form according to the tree species and uneven-aged forest form in area where it is important to increase the amount of qualified water. It is essential to identify future forest structure in order to prepare effective silvicultural prescription and to prepare forest schedule.