KK255,   Many people are confused with these two terms. At one time, the term ADD was commonly used to indicate Attention Deficit Disorder without Hyperactivity. ADHD was used to describe Attention Deficit Disorder with Hyperactivity. However, the correct medical term is ADHD, and this refers to both with and without hyperactivity as these are all considered to be one diagnosis.   Today, people (me as well) often use the term ADD to describe Attention Deficit Disorder with or without hyperactivity, simply because there is one less letter and it is easier to say. This is explained in more detail in ADD or ADHD: Which is Correct?   There are some differences in ADD and ADHD, as indicated in Differentiating ADD and ADHD: Diagnosis, Symptoms and Treatment.   I hope this helps explain this more.   Eileen