Various theoretical grounds for the analysis of volunteering - from the ideas of XIX century classical sociologists to the XXI century theories - are considered in the article. The potential of the structural and functional analysis and conflict paradigms, the theory of exchange and institutional theories is considered as applied to studying volunteering as a system and as an institution. Social action theories, the theory of social movements, as well as social capital theory and social trust theories are stated to be preferable in the development of classical researchers' ideas on understanding the essence of volunteering as activity and community.