Rare diseases are an important medical and social issue. Although the prevalence of individual diseases is by definition low, in aggregate the number of people affected by a rare disease is considerable. These conditions are characterized by severe, debilitating symptoms that substantially affect life expectancy, physical and social functioning, and quality of life of patients and their families.  The question of what constitutes value for rare disease drugs, and how this should be evaluated, is central to the successful continuation of the orphan drug market, and to properly support asset value-based pricing. The objective of this work was to provide preliminary insight into the elements of value which are important when assessing rare disease treatments and how they might be considered together within a value framework. A literature review sought to identify elements of value that are currently considered by European payers when assessing rare disease treatments, those described in patient group surveys, and value elements that have been quantified and described empirically for existing drugs. A generic conceptual value framework was derived based upon the literature review, and this was tested with rare disease experts, patient group representatives, and payers.  Multiple criteria are considered in assessing the value of rare diseases treatments, including burden of disease, therapeutic benefit, familial and societal impact, and economic and budgetary implications. Scientific innovation was also considered, but primarily as a supporting rationale for therapeutic benefit. Clinical/social outcome anchored evidence and data uncertainty were seen to be key factors in determining perceived value.  In future, payers will need to develop assessment frameworks that better reflect the societal value of treatments for rare diseases.  This value is perceived through multiple domains that are not always incorporated in current payer mechanisms. Multi-criteria decision analysis offers a possible construct for incorporating these elements in future.