Addictive behaviours invite us as clinicians and researchers to focus at all times on the subject hidden behind the addictive object, particularly during the process of subjectivation embodied by adolescence. This article is the fruit of international comparative research to explore the prism of personalities of adolescents and young adults with addictions living in France, Switzerland, and Quebec. This study involved 94 participants, aged between 14 and 32. They were divided into a clinical group (54 subjects) and a control group (40 subjects). The methodology consisted of two complementary instruments: the MMPI-A personality test and the CaMIR attachment self-report questionnaire. The results highlighted personality traits common to all three countries: depression, psychopathic deviance, anxiety, social discomfort, social alienation, and physical complaints. They also showed the predominance in all addicts of insecure attachment (detached rather than preoccupied). There were also variations between countries. The Swiss and French young people share a particularly low level of hypomania and a high level of social introversion, whereas the Quebec data showed paranoia as a distinctive trait. The results will be discussed from an institutional perspective in particular, taking into account the treatment practices available to young addicts in the three countries in our study.