Finland has launched a new policy programme to encourage conservation of forest biodiversity, based on economic incentives and voluntarism on the part of non-industrial private forest owners. This study examined the factors that affect the acceptability of biodiversity conservation contracts and the amount of compensation needed in private forests, using the choice experiment method. Data were collected by surveying 3000 Finnish private forest owners. Analysing separately those respondents who were willing to enter into a conservation contract allowed an assessment of the impact of forest owners' heterogeneity on compensation amount.