This report brings together, for the first time in Europe, an integrated overview of the prevalence of intensive cannabis use, defined as daily or almost daily cannabis use (use on 20 or more days in the month preceding survey). Self-reported data regarding frequency of cannabis use from large, probabilistic, nationally representative samples of general population surveys from 20 countries, representing more than 83 % of the population of EU and Norway, were collected through two rounds of ad hoc data collection in 2004 and 2007 and through a routine, standard data collection instrument since 2010.