Non-profit organizations have an important role in democracy development, volunteering and in providing support for disadvantaged social categories whose access to social and medical services or to goods of current necessity is reduced. Recent studies prove that local social sustainability correlates to non-profit organizations density at a local or regional level. Previous research encompasses two directions for the study of the role of non-profit organization the first is supported by the Theory of Government and Market Failure, and the second by the Theory of Voluntary Failure. The Theory of Government and Market Failure starts from the assumption that non-profit sector developed as a result of the need for social services provided to categories of population for whom government and market failed to provide to an affordable price or constantly. The Theory of Voluntary Failure starts from the assumption that non-profit sector plays the most important role in case of socio-economic crises or catastrophes but for organizations to perform well the support of the state is needed. This research aim is the assessment of non-profit density correlation to economic development and percentage of the social vulnerable population in Romania. This paper brings theoretical contribution to the study of the non-profit density, to the Theory of Government and Market Failure and to the Theory of Voluntary Failure and practical implications to an emerging economy.