The inattentive type of ADHD as a distinct disorder: What remains to be done.

I commend Milich and colleagues for their well-reasoned position that the predominantly inattentive type (PIT) of ADHD is a distinct disorder, not a subtype of ADHD. Several issues pertain to future research. Among these are the need to recognize that attention is multidimensional such that several distinct disorders of attention are likely to be identified besides ADHD, one now being PIT. Of great immediacy is the need to expand and refine the symptom list that best distinguishes this disorder from others and to pursue neuropsychological studies using double-dissociation methods that can elaborate the unique psychological domains affected by PIT. In doing so, it will be critical to identify the domains of impairment adversely affected by PIT.