This paper examines the discriminative validity of the Learning Efficiency Test II (LET-II; Webster, 1998) in distinguishing among children diagnosed as having ADHD (Attention Deficit Hyperactivity Disorder) only, ADHD and an accompanying learning disability, ADHD-predominantly inactive type, and a control group. Children (N=132) between the ages of 8 and 16 who referred to a private clinic for psychoeducational evaluations participated in the survey. Each of the participants in the attention deficit groups had been previously identified by at least two professionals as having the specific disorder. Participants for the control group were children referred for other reasons such as underachievement, family problems, or emotional concerns. Analysis determined that the LET-II provided an overall discrimination rate of 57.6% in distinguishing among the four groups of learners. In addition, when comparing the simple dichotomy of the combined ADHD groups as being distinguished from the average group, the LET-II correctly identified 78 of 93 total participants, to yield an 83.9% accuracy rate in distinguishing between ADHD and the non-ADHD group. The data suggests that ADHD may be a disorder involving some kind of atypical cognitive processing where the child is unable to access and retrieve information from either short-term and/or long-term memory stores quickly and efficiently. (JDM)