I've always thought they were similar but an anxiety attack would build up over a longer period of time. Whereas a panic attack would be a more sudden onset of symptoms.

My panic attacks often come out at random times. They're usually completely unseen until you're in the middle of one. Anxiety attacks, like Quillathe said, are usually a build up of anxiety.

An anxiety attack is a general term that has no specific definition, different people can use it to describe different things. A panic attack is a medical term for an episode of intense anxiety accompanied by at least 4 of the following symptoms (listed below). Panic Attacks can be triggered by a specific situation(s) that cause someone anxiety, and they can also happen completely randomly with no warning. At least 4 of these symptoms are required: - Palpitations, pounding heart, or accelerated heart rate - Sweating - Trembling or shaking - Sensations of shortness of breath or smothering - A feeling of choking - Chest pain or discomfort - Nausea or abdominal distress - Feeling dizzy, unsteady, lightheaded, or faint - Feelings of unreality (derealization) or being detached from oneself (depersonalization) - Fear of losing control or going crazy - Fear of dying - Numbness or tingling sensations (paresthesias) - Chills or feeling too hot A panic attack can also cause additional symptoms that are not on that list, but they don’t “count” toward the 4 required symptoms. A panic attack can last a few minutes, or even for several days straight. Some people describe their panic attacks as mild, while others can have clinically-extremely-severe attacks. Panic Disorder is a condition in which a person experiences repeated panic attacks, and at least some of the attacks are completely random. It can also range from mild to extremely severe. My Panic Disorder was extremely severe for years, and has gradually become mild instead (Thank God).