The critical features of ADHD are dysregulated attention and impulsivity. These may impact processing speed, and some research now is indicating that it may be a core deficit in some types of ADHD, but it is not yet clear if it is a cause or effect. Regardless, the current diagnostic criteria do not include processing speed, just attention problems and impulse control problems, often manifested as organizational/executive function issues.

...pronounced like the long vowel and first letter of the alphabet...