Introduction: According to the Accountability for Reasonableness framework, healthcare coverage decisions must be made based on reasons that ‘fair-minded’ stakeholders agree are relevant to resource allocation. We intended to explore this Relevance condition for legitimacy with respect to decision criteria and their selection, using rare disease and regenerative therapies (RDRTs) as a case study. Methods: Features of decision-making processes related to the relevance of decision criteria were defined, including 17 potential criteria, which were identified based on a review of seven published multicriteria frameworks proposed to be applicable for the appraisal of interventions targeting rare diseases. Seven experts from six countries explored and discussed these features during a panel (Chatham House Rule) and provided general and RDRT-specific recommendations for each feature. Responses were analyzed to identify converging and diverging recommendations. Results: Among 17 potential criteria, 13 were recommended by more than half of the panellists. Comparative efficacy/effectiveness, Comparative PROs, Comparative safety, Budget impact, affordability and opportunity costs, and Feasibility of implementation gained the greatest support (≥6/7 panelists). The use of the cost-effectiveness ratio as a principal decision criterion across disease areas was viewed as problematic, particularly when applied to RDRTs due to ethical and methodological challenges. Considering the Feasibility of implementation was deemed essential, especially for rare disease therapies, to ensure that potential benefits are realized in clinical practice. Disease severity was also recommended by most panelists (5/7), as it raised awareness of the goal of healthcare and reflected broadly shared social values. Conclusions: A wide range of decision criteria can be considered relevant for coverage decision-making in RDRTs. Panelists recommended that criteria selection should engage the wider public and rest on the goals of sustainable healthcare and the laws and values of society.