ADHD vs ADD
ADHD is related to ADD, but different. Let’s set out the difference below:
ADHD includes the symptom of physical hyperactivity or excessive restlessness–that’s the “H”. In ADD (or what is called in the diagnostic manual, ADHD, inattentive subtype), the symptom of hyperactivity is absent. Indeed, people with ADD can be calm and serene, not in the least hyperactive or disruptive.
So basically the difference in the “H” of Hyperactivity.