The Nordic countries represent an institutional setting with tax-based health care financing and universal access to health care services. Very few health care services are excluded from what are offered within the publically financed health care system. User fees are often non-existing or low and capped. Nevertheless, the markets for voluntary private health insurance (VPHI) have been rapidly expanding. In this paper we describe the development of the market for VPHI in the Nordic countries. We outline similarities and differences and provide discussion of the rationale for the existence of different types of VPHI. Data is collected on the population covered by VPHI, type and scope of coverage, suppliers of VPHI and their relations with health providers. It seems that the main roles of VPHI are to cover out-of-pocket payments for services that are only partly financed by the public health care system (complementary), and to provide preferential access to treatments that are also available free of charge within the public health care system, but often with some waiting time (duplicate).