BIG HUGE PROBLEM for me too
this is what I did after taking Dr. Phils no fail environment test and scoring a 13 where he recommends a 2. I had it all on a specific shelf in the pantry (snack shelf) and divided it, my stuff -- their stuff. well, their stuff just always looked so much better. Than I took to heart that I'm not really doing them any good letting them each so much junk, but I don't feel I need to get it totally out of the house b/c they are fine with their weight and I didn't want to make a huge issue with a pre-teen DD. So I bought a "washtub" thing at Meijer, open tub - no lid. I put all the "hard-core" junk -- i.e. chips, candy, cookies -- and took it down to our basement pantry. I said that's the junk food tub and you can have one snack per day from it.
Truthfully my DDs went almost a week before remembering it.
I also took to heart Dr. Phil saying once you stop eating the hard core junk so much you really do lose your taste for it. I nodded when I heard him say that (audiobook UWS) and thought if it is true for me it'll be true for them too. Outta sight -- outta mind and eventually they'll lose their taste for it as well.
NOTE: I did restock the snack shelf with more nutritional snacks, some a bit "junky" but not as bad -- i.e. trail mix, pudding cups, granola bars, applesauce tubes, peanut butter, crackers, graham crackers, marshmallows.