The WJIII is not really intended to be a diagnostic instrument for ADHD. The assessments you had/will have that are more directly relevant to ADHD: K-CPT, CEFI, Connors, Brown ADHD. Other than K-CPT, most of them are indirect measures (rating scales). It's a little tricky Dx'ing ADHD in very young children, as a lot of the concerning behaviors are developmentally within the range, and also because so much of young child behavior is affected by the adult-created environment.
All that being said, the kind of WJ cog and ach tasks that tend to be more vulnerable to weaknesses in sustained attention tend to be timed tasks (which also tend to be repetitive), and memory tasks. It is not, however, totally strange for a child who actually has ADHD to do well on these, since it's not as hard to recruit attention and impulse control for a few minutes at a time. Nor do weak scores in these areas necessarily mean ADHD, as there are many other possible causes.
