The implementation of REDD+ requires knowledge of the willingness to accept land use change contracts and its application over large areas. This paper uses primary data from Indonesia to contrast two approaches to the elicitation of the supply curve for carbon: an auction and an analysis of opportunity costs. The analysis shows that there are important differences between the two approaches for a wide range of prices. An analysis of bidding behavior shows that location and individual preferences (time and risk preferences), but not opportunity costs, play a significant role in this decision. The implications for targeting are discussed.