Cannabis is currently the most commonly used illegal psychoactive substance amongst young people aged between 15 and 24, and it seems that 5% of this age group is addicted to it. Many research teams focused particularly on the cognitive disorders caused by cannabis use. Amongst the cognitive functions considered, memory-related, attention-related, psychomotor and motivation-related functions were proved deteriorated by acute and chronic cannabis use; a very important point, especially among teenagers, as possible alteration at the social and academic level could be the outcome. However studies on long-term and persistent cognitive effects haven't provided convergent conclusions. Methodological differences could partly affect these observations. Therefore it seems necessary to develop studies with larger samples.