BACKGROUND There is increasing recognition that conventional appraisal approaches may be unsuitable for assessing the value for money of rare disease treatments (RDTs). This research examines whether supplemental appraisal processes for RDTs are needed, and if so, what form should these take. A qualitative research design was used that included (1) documentation of country appraisal/reimbursement processes for RDTs via questionnaires, desk research and iterative interactions with country experts to produce country vignettes, and (2) a cross-country analysis of these processes to identify and characterise countries with supplemental processes for RDTs, and compare them to countries without supplemental processes. RESULTS Thirty-two of the 37 invited countries participated in this research. Forty-one percent (13/32) use supplemental processes for RDTs. Their level of integration within standard processes ranged from low to high, characterised by whether they are separate or partially separate from the standard process, adapted or accelerated standard processes, or standard processes that account for rarity. They are characterised by features implemented throughout the appraisal process. These features are mechanisms that allow application of different standards to assess the value of the medicine, support to the appraisal/decision-making process, overcome the issues of lack of cost-effectiveness, or exempt from part of/the full HTA process. They apply to ultra-RDTs and/or RDTs, and are often combined. They increase the likelihood of reimbursement by adjusting and/or foregoing part of the assessment process, or accepting to pay more for the same added benefit as for common conditions, which is likely to lead to accepting high prices. A large proportion of countries with standard processes include one or more of these features (formally or informally) or are discussing potential changes in their systems. CONCLUSIONS Results suggest revealed preferences to treat RDTs differently than conventional medicines. Some of the challenges around uncertainty and high price remain, but supplemental process features allow for more adapted and consistent decision-making. Many of these processes are new and countries continue to adjust as they gain experience. These results do not outline what an ideal process for RDTs looks like, but identify some key features that can be implemented to facilitate this process.