Although a relationship between attention-deficit/hyperactivity disord
er (ADHD) and academic underachievement has been widely reported, the
nature of this relationship has not been specified. The present invest
igation addresses this relationship directly by comparing 24 students
(20 males and 4 females) with ADHD and 20 students (15 males and 5 fem
ales) with attention-deficit disorder without hyperactivity (ADD/noH)
referred to a university-based diagnostic clinic for comprehensive neu
ropsychological assessment. The students ranged in age from 6 years 0
months to 12 years 10 months. Consistent with previous reports, this s
tudy found that math achievement test scores for students with ADD/noH
were significantly lower than those for students with ADHD. These fin
dings support previous research suggesting the ADD/noH may represent a
distinct ADD subtype. It is hypothesized that inattention interferes
with students' ability to master abstract symbol systems, especially i
n the acquisition of basic arithmetic skills in the primary grades.