The operational diagnostic criteria for ADHD or HKD were not at hand in Denmark before 1994, when WHO's International Classification of Diseases -10 (ICD-10) was introduced. The criteria for ADHD/HKD were well known at our clinic, but when treating children with stimulants the criteria used clinically prior to 1994 were less specific than today. The aims of this paper are to examine the prevalence of ADHD in a historical cohort of children treated with stimulants during the period 1969-1989 and to reassess a wide range of comorbid disorders and sociodemographic characteristics in order to compare aspects of the given treatment with the modern recommendations. At our clinic 208 children (183 boys) were given stimulants during the period 1969-1989. Case records on these probands were reassessed retrospectively for DSM-IV criteria regarding ADHD and comorbid disorders as well as for characteristics of stimulant treatment. Sixty-five percent met full criteria for an ADHD diagnosis. Including Subthreshold ADHD as many as 81 % of the cohort were re-diagnosed with ADHD. Prevalence rates of conduct problems and anxiety disorder were similar to previous prospective ADHD studies. The use of stimulants during the period 1969-1989 were in accord with modern guidelines. This cohort is comparable to other clinically based ADHD cohorts as regards inattentive, hyperactive/impulsive symptoms, comorbidity, impairment, gender differences, intelligence and socio-economic status (SES).