At the turn of the last two decades of the 20th century, major changes occurred in the social, political and economic systems of Central and Eastern European countries. Authors in their paper relate to the economic fundamentals of a state in the conditions of a mixed economy. They note that in this type of an economic arrangement, private sector co-exists along with the private sector, and economic activities are being carried out via market mechanisms as well as public institutions. The aim of the paper is to identify and define the nature and structure of the public sector, because in our opinion the existing defmitions no longer correspond to recent circumstances. On this basis, then determine whether the scope of the public sector is adequate to its importance. The task is to analyse how broadly the public sector should be conceived, whether it should or should not include along with pure public goods a large scale of mixed goods. Exclusion of mixed goods from public sector domain would mean a gradual reduction in the scope of public goods in the direction towards pure public goods and re-examination of the question of what the relationship between public administration and public policy is. The paper employs several methods, including economic analysis as a scientific approach that deduces, respectively predicts certain phenomena and forms of economic behaviour of the entities in the private and public sector, disaggregation and statistical analysis to measure the size of the public sector domain in the EU countries. Method of comparison was applied to identify common characteristics of the subjects in the mixed economy.