Aims To examine cannabis use among mid-adolescents in 31 countries and associations with per-capita personal consumer expenditure (PCE), unemployment, peer factors and national rates of cannabis use in 1999. Design, participants and measurement Nationally representative, self-report, classroom survey with 22 223 male and 24 900 female 15-year-olds. Country characteristics were derived from publicly available economic databases and previously conducted cross-national surveys on substance use. Findings Cannabis use appears to be normative among mid-adolescents in North America and several countries in Europe. The life-time prevalence of cannabis use was 26% among males and 15% among females and was lowest for males and females in the former Yugoslav Republic (TFYR) of Macedonia: 2.5% and to 2.5%, respectively; and highest for males in Switzerland (49.1%) and in Greenland for females (47.0%). The highest prevalence of frequent cannabis use (more than 40 times in life-time) was seen in Canada for males (14.2%) and in the United States for females (5.5%). Overall, life-time prevalence and frequent use are associated with PCE, perceived availability of cannabis (peer culture) and the presence of communities of older cannabis users (drug climate). Conclusions As PCE increases, cannabis use may be expected to increase and gender differences decease. Cross-national comparable policy measures should be developed and evaluated to examine which harm reduction strategies are most effective.