Gay and bisexual men and other men who have sex with men (GBMSM) with problematic chemsex (a specific sexualized drug use pattern) face several health issues. The aim of this monocentric observational study was to assess mental health history and attachment style (AS) within 71 GBMSM seeking care for problematic chemsex. Attachment style (AS) was evaluated using the Relationship Scales Questionnaire. 82% of the cohort (58) had at least one mental health disorder (among depression, anxiety, alcohol use disorder or hypersexuality). 9.9% were admitted to intensive care due to chemsex use. Traumas were frequent, with 31% reporting childhood sex abuse and 24% declaring having attempted suicide. 62 (87%) had insecure AS: 38% preoccupied, 23% fearful and 24% dismissing. Users with a positive self model (N=24) had fewer comorbidities (63% vs 92%, p=0.003) and practiced more chemsex alone (75% vs 33%, p<0.001) than users with negative self model (N=47) . Users with a positive other model (N=35) practiced more slamsex (injections of substance in a sexual context) ( 80% vs 50%, p=0.008) and had fewer comorbidities ( 71% vs 92%, p=0.027) than users with negative other model (N=36). Attachment theory is a way to provide holistic and tailored and harm reduction.