Attention deficit hyperactivity disorder (ADHD) manifests as a behavioral pattern that leads to significant social, educational and occupational impairment. The main characteristics of the disorder are inattention, hyperactivity and impulsivity 1. The diagnosis of ADHD is clinical and is based on a persistent, early-onset clinical picture that manifests in different settings and leads to functional loss 2 . A failure in behavioral inhibition is believed to lead to the predominant symptoms of ADHD: hyperactivity, inattention, distraction and impulsivity 3 . The changes in the catecholaminergic pathways are believed also to involve the nucleus accumbens, with impairment of selective attention and the reward system 4 , which may be associated with a greater risk of substance use and dependence 5. The risk of dependence on alcohol or other substances is significantly higher in adolescents with attention-related difficulties than in healthy adolescents 6. Hence, because of the impulsivity and inattention associated with the condition, ADHD may be a risk factor for substance use disorder 5 , a set of cognitive, behavioral and physiological symptoms that cause occupational impairment as a result of the use of a particular substance. Substance dependence is a clinical condition at the more severe end of the substance use disorder spectrum. Even when occupationally incapacitated, dependent individuals continue to use substances. Drugs described as potentially causing dependence include nicotine, alcohol, cannabis, and cocaine and its derivatives ABSTRACTObjective: Attention deficit hyperactivity disorder (ADHD) is characterized by a persistent pattern of inattention or hyperactivity. This study aimed to investigate the relationship between ADHD and drug dependence. Methods: The presence and severity of ADHD and substance use were evaluated through questionnaires in 80 adult patients in therapeutic communities. Results: No difference in drug use or dependence prevalence between ADHD and non-ADHD patients was found. However, ADHD patients had lower ages on admission (p = 0.004) and at first contact with cocaine (p = 0.033). In ADHD patients, there was a negative correlation between the age at first use of cannabis and the subsequent severity of cannabis use (p = 0.017) and cocaine use (p = 0.033). Conclusions: Though there was no difference in prevalence of drug use among groups, results show that ADHD in patients in therapeutic communities may cause different addiction patterns, such as earlier use of cocaine and admission, and a more severe use of cocaine correlated to earlier contact with cannabis.Keywords: attention deficit disorder with hyperactivity; substance-related disorders; cocaine. RESUMOObjetivo: O Transtorno de Déficit de Atenção e Hiperatividade (TDAH) é caracterizado por um padrão de desatenção ou hiperatividade. Este estudo investigou relações entre TDAH e dependência de substância. Métodos: Prevalência e gravidade de TDAH e de uso de substância foram avaliadas em oitenta pacientes adultos de comunidades ...