By employing multiple regression analysis, the article identifies the social, economic and political determinants of overall private education expenditure and private spending on tertiary education in 26 OECD countries, testing hypotheses derived from theories of comparative public policy. We find that overall private education expenditure is higher in federal countries and under Conservative parties in government, while it is lower where voters prefer state-centred solutions, where Catholicism is strong and where a Church tax exists. Analysing private expenses for tertiary education only, these findings reappear with one exception: the size of the student population, which is without substantive effect on general private education expenditure, yields the largest single effect in the tertiary sector. [ABSTRACT FROM AUTHOR]