The Portuguese health system has been characterized by the existence of a constant relationship between public and private sector, both in providing and financing health care. In recent decades, the private sector increased their responsiveness of care, extending the engagement in the relationship with the public sector. This relationship stems from the legal framework set out in the law, developing agreements, conventions and more recently through the model of public-private partnerships. In hospital network, this new dynamic relationship contributed, in the last two decades, to accentuate the mixed characteristics of the system, through a clear strengthening of the private component in the hospital network, particularly by investing in differentiated units.