The research comprises a combination of 'closed oral interviews' (N= +_500) and 'in-depth interviews' (N= +_50). The first interviews will give a description of the forest owner and his forest and will determine the attitudes of the forest owners towards some specific measurements concerning sustainable forestry. Also their motivation come to a specific attitude will be analyzed. The in-depth interviews will emphasize the research on these motivations, based on the 'Theory of Planned Behaviour'.