This paper presents information on the diagnostic criteria and management of disorders that may be wrongly identified as Attention Deficit Hyperactivity Disorder (ADHD) or may coexist with ADHD thus complicating identification and treatment. The disorders discussed are: depression, mania, primary disorder of vigilance, narcolepsy, developmental specific learning disorders, conduct disorders, and acquired neurological deficits. The introduction briefly reviews the history of ADHD identification and treatment. A study in which 100 referred children (ages 3 to 17) were systematically examined found ADHD criteria were met in 63 of the children but only four had ADHD alone. Forty of the children had both developmental specific learning disorders and depression as well as ADHD. Two longitudinal studies reporting relationships between hyperactivity and depression and between learning disability, depression, and ADHD are also briefly reported. Each of the other disorders is discussed including criteria for diagnosis, course of the disorder, biological correlates, the presence of concurrent disorders, and treatment approaches. It is noted that methylphenidate and pemoline, often prescribed for children doing poorly in school, can decrease hypomanic symptoms and improve vigilance but worsen or induce depression. Prognosis for children and adolescents with primary affective illness is reported to be good with appropriate management. Includes 84 references. (DB)