Treaties are categorical as to the limited competencies of the European Union when it comes to health policy. However, this statement is not true for complementary and supplementary health insurance, which accounts in several European countries for a significant share of health expenditures – and when it is even the main provider of care for some benefits. In this respect, private (usually voluntary) health insurance has been fundamentally transformed by a series of European directives and regulations over the last thirty years. But how and to what extent EU legislation changed the nature of private health insurance from a country to another? How these policies interacted with other legislations and policies at the national level? Based on a comparison between four European countries (Belgium, Ireland, France and The Netherlands), we argue that this process resulted in decoupling between the insurance and healthcare regulations. This, in turn, has become a major source of policy feedbacks and unexpected outcomes of reforms affecting the healthcare sector at the national level, yet with contrasting results from a country to another. Together, these changes are likely to change the provision of care and to reduce individual welfare.