As programs with payments for ecosystem services (PES) have become more numerous, raising the need for and also the opportunity for rigorous evidence on their contributions, we examine shifts within Costa Rica’s Pagos por Servicios Ambientales (PSA) program. The PSA was heralded from its initiation, despite demonstrations of low early impacts. We study shifts in impact over time across early periods and whether further adjustments could raise contributions. Looking over time, we find that PSA contracts signed for the 2000–2005 period had higher impacts than contracts for the program’s initial time period, 1997–1999 found in previous research. Looking over space, we find that PSA payments have higher impacts for lower slopes and lower market distances. Linking these results, the rise in impact for 2000–2005 occurred alongside a shift in the targeting of PSA, which was along ecological dimensions (limiting effects of owners offering unprofitable lands). Yet the spatial variations in impacts we document suggest that explicitly targeting impact offers the potential to further raise PES impacts in Costa Rica, as well as in other nations.