Neuropsychological tests were used to evaluate different memory systems in the three subgroups of adult Attention Deficit Hyperactivity Disorder (ADHD) (n=105) using analysis of means, factor analysis, and GLM analysis with covariance of gender, estimated IQ, and level of anxiety and depression measured with the Hospital anxiety and depression scale. A higher IQ level was found in the neuropsychological background tests for the predominantly inattentive subtype (ADD). In the memory tests the dual-task memory/simultaneous capacity tests "Brown-Peterson" Consonant Trigram and Benton Visual Retention Test (BVRT) were the most sensitive and were severely reduced in all three subgroups, but only the BVRT revealed a difference between the three ADHD groups. In learning and delayed recall measured with Rey Auditory Verbal learning test and modified Diagnosticum für Cerebralschädigung (mDCS), the Attention Deficit Disorder subgroup had the best learning and delayed capacity of the three groups. A good agreement was found between the interviewed DSM-IV-TR criteria, Conners CAARS S:S scale, and Wender WURS 25-item scales. Despite the difference in number of ADHD criteria for the three ADHD subgroups, the results in the neuropsychological memory tests indicate a severe reduction in all three subgroups of adult ADHD in simultaneous capacity.