Development of children aged 5 to 12 years born to mothers with heroin dependency raised at home or adopted was studied in comparison with: (1) children with environmental deprivation alone (i.e. low parental socioeconomic status [SES] and evidence of neglect), (2) children born to fathers with heroin dependency fathers, and (3) control individuals of average SES. One hundred and sixty children (84 males and 76 females; average age at examination 8 years) were evaluated between 1998 and 1999. All were attending mainstream schools. All participants were examined by a paediatrician and a psychologist using standard neurological and psychological age-appropriate tests, as well as tests and questionnaires to assess learning ability and attention span. The Conners and Achenbach questionnaires and the Pollack Taper test were used to assess possible presence of attention-deficit–hyperactivity disorder (ADHD). Mothers were assessed for ADHD using Wender's questionnaire. Children born to parents with heroin dependency raised at home and those of low SES exhibited intellectual impairment both on verbal and performance skills. They also had impaired reading and arithmetic skills. Children born to mothers with heroin dependency but who were adopted at a young age had normal intellectual and learning abilities, except for some reduced function on the performance Wechsler Intelligence Scale for Children–Revised. We found a high rate of ADHD among all children born to parents with heroin dependency, including those adopted, as well as in children with low parental SES. The highest rate of ADHD was in children born to mothers with heroin dependency raised at home, being twice that observed in the other groups. Mothers of these groups of children also had a high rate of ADHD.