Cannabis is the illicit drug most widely available in Europe, where it is both imported and produced domestically. In most European countries, cannabis use increased during the 1990s and early 2000s. Europe may now be moving into a new phase, as data from general population and school surveys point to a stabilising or even decreasing trend in cannabis use in many countries. Levels of use, nevertheless, remain high by historical standards. The last few years have also seen a growing understanding of the public health implications of the long-term and widespread use of this drug, and rising levels of treatment demand for cannabis-related problems. Therefore, what constitutes an effective response to cannabis use remains a key question in the European debate on drugs.