ADHD and ADD are often used interchangeably. There’s a slight difference between the two. ADD is a type of ADHD, which doesn’t involve hyperactivity or impulsiveness. It is used to describe the inattentive-type of ADHD. That said, ADHD is a more common medical term now, often used by doctors irrespective of hyperactivity symptoms in the patients. The use of the term ADD is obscure and outdated.