PURPOSE: Few studies have explored the prevalence of psychiatric disorders (PD) among university students. This article aims to study 12-month prevalence of PD in university students, their socio-economic correlates, impairment in daily life and help-seeking behaviours. METHODS: Cross-sectional study of randomly selected first-year students aged 18-24 years, enrolled in one of the six universities in south-eastern France in 2005-2006. We used the WHO CIDI-Short Form to derive DSM-IV diagnoses and the Sheehan disability scale to evaluate impairment. We studied their correlates with multiple logistic regressions. RESULTS: The 12-month prevalence of major depressive disorder (MDD), anxiety disorders (AD) and substance use disorders (SUD) were 8.9% (95% CI: 7.2-10.9), 15.7% (95% CI: 13.5-18.2) and 8.1% (95% CI: 6.7-9.8), respectively. MDD was associated with precarious economic situation (OR = 1.83; 95% CI: 1.03-3.23), AD with a precarious job or unemployment of the father (OR = 2.08; 95% CI: 1.04-4.14) and SUD with higher educational level of father (OR = 2.17; 95% CI: 1.28-3.67) or having a paid job (OR = 1.82; 95% CI: 1.06-3.13). "Marked" or "extreme" impairment (score > or =7 for at least one of the domains in the Sheehan scale) was noted for 51.7% of students presenting a PD and was even more frequent in the presence of MDD/AD comorbidity. Only 30.5% of the students with a PD had sought professional help in the past 12 months. CONCLUSIONS: This study provides new results regarding university students suggesting a link between precarious economic situations and MDD. The frequent impairment arising from PD alongside low rates of help-seeking suggests that PD could be one of the factors in academic failure in first year of university. These results should be used to improve prevention and care of PD in university students in France.