Introduction: Young adults, particularly those aged 18–25, are rarely studied in terms of their use of psychoactive substances in France, and even less so when they are college students. However, studying these age groups—situated between adolescence, a period of experimentation with substances, and adulthood, when such use may become established in daily life—is essential to understanding the integrated use of these substances. Methods: A sample of students from a Parisian university was surveyed via self-administered questionnaire during the academic term, comprising 869 first- and second-year students across five major disciplines: medicine, pharmacy, law, psychology, and sociology. Results: One in two students has already experimented with cannabis, with significant differences between men and women—55.2% versus 45.7%, respectively—depending on the high school track: 39% of science track graduates versus 59% of economics and social sciences track graduates and 63–72% of vocational track graduates, and depending on the university major: 25.9% in pharmacy, 37.3% in medicine, and 41% in law versus 72% in sociology and 65.2% in psychology. The age at which students first tried cannabis is close to 16, with significant differences depending on the type of high school diploma and the father’s occupation and socio-professional category. One in three students had used cannabis in the year prior to the survey (33.4%), one in six in the past month (16.3%), and 13.6% of students had experienced problematic cannabis use at some point in their lives. (R.A.)