The purpose of this study was to estimate differences between perceived and reported drug use among sophomore and junior university students, aged 18 to 24 years, from a public university in Medellin, Colombia.this is a descriptive and cross-sectional study. All second- and third-year students at the Schools of Medicine, Dentistry, Nursing and Public Health were invited to answer an anonymous questionnaire. In total, 427 students participated.data suggest that students overestimate the use of tobacco, marijuana and cocaine over the last 12 months. Alcohol use was perceived accurately. Students who reported using those substances during that period overestimated their peers' drug use more than those who did not. Furthermore, more women than men overestimated marijuana use.