A new approach to volunteer motivation research is developed. Instead of asking what motivates the volunteer (accepting "any" conceptual category), we ask to what extent volunteering rewards the individual with each benefit taken from a complete set of possible benefits. As a "complete set of benefits" we use the 16 human functioning modes formulated within the systemic quality of life model (SQOL). Data collected from a large representative sample substantiate the conceptual basis of the approach proposed. Empirical results (by Faceted SSA, a multidimensional scaling technique) support the volunteer-motivation structural hypothesis and highlight the more salient volunteering motivations. Social groups (including volunteers vs. non-volunteers) are compared with respect to their volunteering motivation assessments. The proposed approach sheds new light on theoretical issues, such as the roles of altruism versus egoism in volunteering, and suggests new ways for studying the questions of volunteer recruitment and retention.