There are some differences between a panic attack and GAD.
Panic attacks can be situational and the fear of having an attack can have a person avoid specific situations.
This is not the case with GAD.
Also there is not a sense of "panic" that you get with the other kind of episode.
The strength and physical changes can be a lot stronger with a panic episode.
GAD is more of a slow and gentle type of disorder and gives you a constant sensation that something is wrong.
This differs very much from a panicing episode which some on strongly.
Generalized anxiety disorder gives you a long term thinking and dwelling process.
Another feature of GAD is the exaggeration of a particular situation.
A person suffering from this might spend hours and hours thinking "the worst" about a particular event; especially if it is something unknown.
For example, a sufferer could be sitting at work all day worrying that a child is having something happening at school or is in danger.
And this anxiety drags the sufferer down for the entire day; never going away.
When the truth is revealed and the anxiety is disproven, then the GAD sufferer's mindset will move onto another issue with an unknown situation.
Panic attacks and GAD share many similar qualities.
But the length of time they occur and the severity of them will differ very much.