ENEffectively working third sector is efficient for the development of civil society, which in turn determines the optimized socio-economic development. This article undertakes an analysis of the third sector of two – similar to each other in terms of socio-economic values – Lithuania and Poland. Despite many similarities, these countries still differ not only in the framework of action but also their non-governmental organizations are diverse in terms of their qualitative and quantitative characteristics, as well as challenges, which will they have to met.