The main goal of the work is to identify the factors that influence the non-profit welfare sector among the European Union (EU) countries in order to shed some new lights on the relationships existing between the non-profit sector and the public sector when they both act as providers of welfare services. From our research findings, it appeares that the relative size of the non-profit and public welfare sectors varies significantly among EU countries. Not only do countries vary considerably in the size of their welfare sectors but also they vary in the extent to which these sectors are financially related. Our analysis finds out that is hard to support the prevalence of a specific factor as main determinant of the size of the non-profit welfare sector in EU, mainly when the non-profit is considered as a complex social phenomenon. The evidence here provided also does not confirm the existence of a common and unique European model in the provision of welfare services among the sample countries. Rather, three different models or patterns of relationship between the non-profit and public welfare sectors are evident in Europe.