In this paper, we review Western studies on the prevalence of comorbid attention‒deficit/hyperactivity disorder（AD/HD）in individuals with drug abuse/dependence, and the associations of drug abuse/dependence with AD/HD. Additionally, we introduce our studies on the associations between adulthood drug abuse/dependence and the childhood AD/HD tendency in Japan, using a self‒rating questionnaire to assess childhood AD/HD tendencies, the Japanese version of the Wender Utah Rating Scale.
 Our studies suggested that, while adulthood drug abuse/dependence may be closely associated with the childhood AD/HD tendency, as many Western studies have indicated, the abused substances most commonly chosen by drug abusers with a childhood AD/HD tendency were not methamphetamines but organic solvents, unlike in several Western studies. Our results did not support the findings of some Western studies：“preferences to choose a stimulant as“self‒medication”to directly improve AD/HD symptoms. However, organic solvents appeared to be chosen as“self‒medication”to cope with secondary/peripheral symptoms derived from AD/HD.