Landowner preferences are elicited for different contractual agri-environmental agreements (AEA) using choice experiments in the Portuguese montados, an agro-forestry ecosystem with high conservation value. The choice experiment is developed with the help of biologists from local environmental authorities and builds upon existing AEA in the Portuguese Rural Development Program ProDeR implemented at Natura 2000 conservation sites. Current uptake rates of AEA for montado conservation are very low. The study's main objective is to assess how varying the institutional-economic terms and conditions underlying current contract design can increase this uptake. We find demand for AEA inside and outside the currently designated protection areas, but there exist clear trade-offs between willingness to accept financial compensation and opportunity costs measured through varying cattle and oak tree density levels. Also contract duration plays a significant role. Minimum willingness to accept financial compensation for a hypothetical scenario representing the current contract conditions in the region is more than six times higher than the actual payment levels under the existing agri-environmental agreements.