In this article, we investigate the determinants of job mismatches with regard to the field of education among school-leavers in Europe. We also examine the effects of job mismatches on the labour-market position of school-leavers. Special attention is paid to cross-national differences in this respect. The data used are from the EU LFS 2000 ad hoc module on school-to-work transitions. The empirical results show that a number of individual, structural and job characteristics affect the likelihood of having a job mismatch. Moreover, in countries in which the education system is vocationally oriented, the incidence of job mismatches among school-leavers is higher than in countries in which the education system is mainly general. With respect to the labour-market effects of job mismatches, it is found that school-leavers with a non-matching job achieve a lower occupational status, more frequently look for another job, and more often participate in continuing vocational training than those with a matching one. These labour-market effects of job mismatches are smaller in countries in which the vocational orientation of the education system is stronger.