Payments for Environmental or Ecosystem Services (PES) schemes have become a popular tool to address environmental degradation and to promote sustainable management of ecosystem services. We use metaregression analysis on a sample of 110 individual studies to investigate the determinants of the environmental effectiveness, defined as the probability to increase environmental services (ES) provision, of about 149 PESschemes implemented worldwide. We find that increased effectiveness of PES schemes is strongly associated with periodical third-party monitoring, generic reference design and to a lesser extent results-based payments. We further study the determinants of PES additionality, defined as direct changes in ES provision induced by the PES scheme, compared to a baseline without PES, on a smaller sample of 41 studies from which we could obtain the necessary data. The results confirm the role of certain design variables, such as monitoring type, and raise a potential trade-off between enrolment and additionality in the assessment of PES effectiveness.