How do you define a “pocket gun”? Obviously, this is a very subjective thing and people will have a variety of opinions.
For example, I found this comment on a forum:
For some reason, people like to take compact firearms and try to claim that they are pocket guns. You want a test: here is one. Go into a gun store wearing jeans. Take a gun and put it into your rear pocket. If it can be totally concealed in your rear pocket, then you have found a pocketgun. If a little of it peeks out, then you have a small gun, but not a pocketgun…My personal test as to what is a pocket gun and what is not, is the guns ability to be fully concealed in the rear pocket of a pair of slacks.
Someone else said:
My definition of a pocket gun is one that can actually be carried in,and drawn from, the pocket effectively in public, not merely being able to fit in one’s pocket.
There are some who say they are able to conceal a full-size 1911 handgun in their pocket. I don’t believe it. On the other hand., by strict definition, a pocket gun is any gun that will fit in a pocket. That’s pretty broad and inclusive!
My (Mousegunner’s) personal definition of a pocket gun ties in with the guns usefulness as a concealed weapon. Many a large gun can be stuffed into a pocket. But it will be noticeable, because of its size, thickness and weight.
I define a genuine pocket gun as one that will comfortably fit into a man’s front pants pocket, not be uncomfortably heavy so as to shift around a lot while walking, and not be noticeable to the general public.
I believe these criteria rule out anything that is larger, thicker and heavier than a GLOCK 26 (9mm) or 27 (40S&W;). This is just my personal definition, and of course you are welcome to your own opinion!

Here’s a picture of a Kel-Tec P3AT and P-11 together.
As you can see, the P-3AT is quite a bit smaller. However, the P-11 CAN work as a pocket pistol. It is just a little bit smaller than the GLOCK 26/27.
The Kel-Tec PF-9 (see my review) is just a bit lighter and thinner than the P-11, and works better as a pocket pistol. However, the capacity of the PF-9 is only 7 + 1. The PF-9 is 5.85 inches long, 4.3 inches high, and .88 inches thin. It weighs 12.7 ounces empty. It is said to be the flatest and lightest 9mm pistol available.
I sometimes carry one in my pocket, and in my opinion it is an excellent pocket pistol. It is light, thin, and not very expensive (under $300). If you have plenty of funds, then you may prefer the Kahr PM9 ($650), or the Rohrbaugh 9mm pistol ($950). For about $500 you can get a GLOCK 26 or 27.