The goal of the proposed research is to investigate whether, why and when student work affects later labour market success. First, regarding the whether-question, I will use advanced statistical techniques to measure whether student work experience really has a direct impact on later employment chances or whether the positive relation found by previous studies just reflects positive qualities that were not observable in their research data such as IQ and motivation, potentially leading youngsters to accept student jobs but also to earn more later. Second, regarding the why-question, I propose to test the practical importance of some general economic theories that may explain a direct impact. For instance, I will test whether real world empirics are in favour of the theory stating that student work experience is used by employers as a signal of good qualities they cannot examine based on a written resume. To this end, I propose to send out fictitious job applications, equal in terms of education level and other important characteristics, but differing in whether student work is mentioned, to real vacancies. By comparing the employers’ reactions, the surplus of mentioning student work with respect to hiring chances can be measured. Third, regarding the when-question, I will focus on how the impact of student jobs differs by various characteristics of these jobs such as relation to the field of study and timing (during secondary or tertiary education and during the summer or the academic year).