Understanding landowners’ decisions about how much land to enroll in payments for ecosystem services (PES) programs is essential to strategically target lands for conservation, prevent forest fragmentation, and thus maintain ecosystem services. In this study, we targeted private lands surrounding and connecting public pro tected areas in a deforestation hotspot, the Argentine Chaco forest. We used alternatively configured PES con tracts in choice experiments to understand landowners’ decisions regarding how much land to enroll in PES. We found that factors influencing decisions on how much land to enroll differ from those influencing willingness to participate in PES. The percentage of their property that landowners were willing to enroll in the program increased with higher payments and permitted land use that closely aligned with traditional land use, specifically cattle ranching under tree canopy. Contract length was important in willingness to enroll but not in amount of land enrolled. Payments required to enroll all land in our study area, and thus conserve an unfragmented landscape, exceeded the financial resources of the Argentine PES program. Designing PES to enroll private lands on smaller strategic areas, in conjunction with other conservation initiatives, would be more effective than attempting to use PES alone to conserve large landscapes.