Ecosystem services assessments are increasingly being used to inform marine policy and planning. These assessments involve significant time, effort, and expertise. It is important at the outset to determine which of many ecosystem services should be quantified and which measures of ecological output, economic impact, or value should be assessed. Furthermore, the literature shows that in practice such assessments are unevenly applied and rarely used effectively in decision-making processes. We develop a structured decision-making approach, called a triage, to assess what types of ecosystem services should be assessed to improve the uptake and usefulness of such information in marine planning. Two case studies, in France and the United Kingdom, provide examples of the application of the triage approach.