Cannabis is by far the illegal substance the most widely used by youth aged 12-25 years. One out of five persons living in France has already tried it once in his lifetime. Although the psychiatric symptoms as well as the cognitive and acute or chronic behavioral effects linked to repeated use of cannabis are well documented in the literature, search for persistent cognitive effects amongst chronic users has not provided convincing evidence because of methodological biases. The issue is nevertheless most crucial, especially amongst teenagers, due to the potential risks of deteriorated academic, social and occupational performance. The longer the exposure to the effects of the substance, the greater the risk of complications. Based on data reported in the literature, we report the cognitive effects associated with chronic use of cannabis as well as its social and educational consequences.