This study was designed to evaluate the relationship between the DSM-III criteria for attention-deficit deficit disorder with hyperactivity (ADDH) and the DSM-III-R criteria for attention-deficit hyperactivity disorder (ADHD). Seventy-two children from an inner-city elementary school were evaluated using parent and teacher ratings on a scale consisting of the symptoms of DSM-III-R ADHD and oppositional-defiant disorder and DSM-III ADDH. Each child was also assessed using a psychometric test battery designed to examine cognitive function, attention, and activity level. Teacher ratings identified more children as DSM-III-R ADHD than DSM-III ADDH. Among these ADHD children, those who also met the ADDH criteria missed more targets on a continuous performance test (CPT) and were rated more overactive than controls. They also had a greater likelihood of being rated ADHD by parents. Children rated as meeting criteria for DSM-III-R ADHD, but not DSM-III ADDH, were not substantially different from controls on teacher ratings of overactivity, CPT performance, or parent ratings of ADHD, which raises questions regarding the nature and severity of the pathology in this group.