Biodiversity conservation programs that appeal to landholders' motivations and minimise their barriers to participation may result in both increased uptake rates and improved ecological outcomes. To understand their motivations and barriers to conserve biodiversity, qualitative interviews were conducted with 45 landholders who had participated in one of three different programs in Queensland, Australia. The results revealed that the landholders' decisions to participate depended on the level of formal biodiversity protection offered by the program, potential changes to their property rights, personal benefits of participation, and the program objectives. Landholders' motivations related to conservation, production, financial and experimental imperatives. Common barriers to participation were lost productivity, different interpretations of what constituted "conservation", and limits to future development and land use options. Voluntary and economic policy instruments can be used to stimulate participation and overcome barriers, but must be applied with care to reduce the creation of perverse ecological outcomes, such as slippage and low additionality. (Contains 1 figure and 3 tables.)