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 meta-regression 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 PES-schemes 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.