ObjectiveTo maximize benefits and reduce potential harms of organized cancer screening programs in Europe, monitoring, quality assurance, and evaluation of long-term impact are required. We aimed to identify the most important indicators to be collected and reported. The study was designed to establish a consensus within a European-level working group and suggest a manageable list of key indicators.MethodsWe conducted a Delphi study among policymakers, researchers, and program coordinators who were experts in breast, cervical, or colorectal cancer screening. Study participants evaluated the importance of screening indicators on a 5-point Likert scale.ResultsThe top 10 indicators by study participants were interval cancer rate, detection rate, screening attendance, screening coverage, cancer incidence, cause-specific mortality, proportion of persons attending further assessment after a positive screen test result, proportion of persons attending a treatment after diagnosis, invitation coverage, and distribution of cancers by mode of detection. Performance indicators were generally considered more important than outcome indicators. Subgroup analyses by cancer types showed similar results, and only cervical cancer screening experts had slightly different preferences. Subgroup analyses by experts’ roles indicated that policymakers found different indicators important compared with researchers or program coordinators, probably because of their different point of view on screening.ConclusionThe implication of our priority ranking is twofold: it serves as an initial guidance for countries that have not yet established a system to collect data, and as a checklist for those where data collection is already established, to assess the comprehensiveness of their system.