The aim of this study was to undertake a European comparative analysis of the determinants and the effects of educational investments on the individual level. The focus of the study was laid on secondary education. The project consisted of a literature review and complementary studies. The effects of educational investments depend among others on individual abilities, on the social background, on the quality of educational institutions, on the duration of compulsory education and on the qualification level of the whole labour force. Typically, in the economic literature, educational investments are legitimated by to their contribution to the improvement of individual abilities, productivity and in a macroeconomic view of welfare. This traditional view based on human capital theory has been complemented by the filtering or screening theories. The latter theories assume that not the ability- and productivity-enhancing effect of education is essential, but rather the information it provides for the selection of the labour force to be hired. Both views are relevant from an empirical point of view. Though there is no consensus about this, the extent to which human capital theory arguments play a role as opposed to screening arguments, however, is essential for policy makers.