Objectives: Of the fourteen counties and two municipalities that until recently were responsible for healthcare provision in Denmark, five introduced mammography screening (MS) programs. The objective of this research is to explain this decision-making variation and to gain insight into priority setting processes in health-care provision at the county level in Denmark.

Methods: Literature on priority setting in health care was used to derive seven explanatory factors for comparing decision making on MS between four selected counties, of which two had implemented MS. The relative importance of each explanatory factor in each county was determined by analyzing policy documents, supplemented with interviews of selected stakeholders. The results were combined and compared at the county level.

Results: Evidence of effectiveness of MS was considered satisfactory and ethical issues related to MS were perceived relatively unproblematic only in those counties that introduced MS. Lack of resources, that is, radiologists, was an additional important factor for counties not implementing MS. Local opinion leaders have played a stimulating role, whereas advisory policy documents at the central government level and even legislation have had a minor impact.

Conclusions: The four counties have based their decision making on the introduction of MS on different combinations of a limited number of factors that have been differentially weighted. The pattern of relevant factors in both counties not introducing MS is rather similar. The study elucidates the role of complementary factors to evidence in decision making. Of interest, recent public sector reforms have resulted in the decision to have MS implemented nationwide.