Objectives: To determine whether the nature and correlates of attention-deficit/hyperactivity disorder (ADHD) symptoms are different in subjects with mild intellectual disability (ID) compared to subjects with average ability. Method: From a general population sample of 2,726 12- to 15-year-olds, a stratified subsample was selected to enrich for mild ID. A total of 192 subjects were included in the analyses. ADHD symptoms and other emotional/behavioral problems were measured with the parent and teacher Strengths and Difficulties Questionnaire and IQ with the WISC-III-UK), and social communication difficulties were assessed by a short version of the Social Communication Questionnaire and academic attainments by the Wechsler Quicktest. Results: There was a negative linear relationship between ADHD symptoms and IQ ([beta] = -0.087, p less than 0.001). The relationship could not be explained by inappropriate rater expectations. Neither the profiles of ADHD symptoms nor the comorbidity with emotional/behavioral problems differed according to the presence of ID. When IQ was accounted for, the group difference in attainments was nonsignificant. Conclusions: ADHD symptoms are increased in people with ID. We found no evidence that this increase can by explained by inappropriate expectations or by confounding associations with other emotional/behavioral or cognitive problems. (Contains 4 tables and 1 figure.)