In spite of being a major public health issue, no data on depression in young people exist in Laos. Decision makers are therefore poorly equipped to define the degree of prioritization of this pathology among their preoccupations. This study aimed at estimating the prevalence of depression among last-year high schools students and exploring some of its determinants with a qualitative approach. The quantitative component was based on a survey of a representative sample consisting of 210 students studying in 30 schools in the capital city, Vientiane, using the Beck Depression Inventory validated in the Lao language. The qualitative component was based on interviews with 5 nondepressive and 5 depressive students. Clinical depression prevalence was 24%. Depressed students were aware of the effectiveness of available medication and its importance in controlling the disease. The other students had little knowledge about the disease and how to handle it.