Tallball is right, the frame and cylinder sizes are the same.
I think that the smallest production of late was the Taurus View/No View, but as was pointed out they didn't last long and are now out of production. I can not speak of the .380ACP offering out there as I've never seen one.
I recently picked up a No View and really the only thing smaller than any other five shot 38 out there are the grips and barrel, and in my opinion both are
too small to be of much serious usefulness.
The grip is too small for my size 9 gloved hands, (read: average) to actually get any kind of real grip on.
Typically when a manufacturer offers a small revolver in 32 caliber they up the round count in the cylinder by one using the same frame size as a five round 38.
I suppose that making a five round 32 would save a little diameter on the cylinder, but I doubt that notably much. Any smaller on the grip or barrel under what is already available out there, would be hinging on the 'too small to be useful' size of the Taurus View.
The View didn't go over very well on the market, both offerings only remaining in production for about one year each.
I guess what I'm saying is that I understand the desire for, but doubt much could be reduced in size and still be useful under what is already out there really. I don't believe that the difference would be that great.
When Tammy gets home later I'll take a picture of her Charter Arms 'Southpaw' Pink Lady, (which is about as small as current production revolvers get to my knowledge) next to my Taurus No View and post it, in order to demonstrate what I am getting at.
Picture as promised