Aims:This study sought to quantify the perceptions of damage and benefit, for users and society, associated with five addictive substances (alcohol, tobacco, cannabis, cocaine and heroin) and one addictive behavior (gambling), in a large sample representative of the French population. We compared with expert assessments and investigated the effects of substance consumption on these perceptions. Findings: The ranking of substances by the lay public is very divergent from that of experts. The public overestimates damage to users and to society and underestimates the benefit, in comparison with experts, for all substances. Alcohol is the only exception, with damage and benefit perceptions similar to those of experts. Heroin and cocaine are perceived as the two most dangerous substances. The damage of cannabis and alcohol are judged to be equivalent. The three legal substances are associated with the highest overall benefit, although cannabis has the highest perceived benefit for users. Substances with the highest perceived benefit tend to be associated with perception of lower levels of damage. Individuals with an history of substance use have a perception of the damage and the benefit for that substance which is more congruent with experts, including a similar ranking of substances. Conclusions: Prevention campaigns focused on perceptions of damage alone have reached their limits. The perception of benefit should be taken into account in early interventions with illegal substance users.