The management of biological diversity at the landscape level in Finland is complicated by the relatively small size of the holdings and the fact that the habitats of species do not necessarily follow the holding borders. Therefore, there is a great need to develop such forest-planning approaches that aim at solving the problems that some species have faced due to modern forestry, including the fragmentation of old forests. One way to deal with fragmentation is to aggregate old forests into larger patches, a goal that may be achieved by excluding some areas from forestry operations or by restricting the intensity of treatments. In a planning area under multiple ownership, the sizes, shapes and relative locations of set-aside areas are important, since they affect the social equity of the proposed forest plans. In this study, the effects of two conflicting goals, i.e. the improvement of old-forest patterns, and the equal participation of forest owners were studied in a privately owned forest area in Finland. This was made possible through the examination of the consequences of alternative strategies to delineate areas set aside. The two main results of the study were, first, that it is difficult to reach these goals simultaneously, and, second, the time interval relevant in the management planning of private forestry is quite short with respect to efforts to change landscape structure significantly. However, in real planning situations, it is important to specify the locations of forest holdings whose owners are willing to acknowledge biodiversity values above the level defined in the legislation. In addition, ecologically important areas should be located and connected to the above information. According to the results of this study, it seems that a compensation system would facilitate the restructuring of the forest landscapes towards an ecologically enhanced structure.