http://forum.doityourself.com/showthread.php?t=221960Most of the closet organization systems I work with are about 15 inches out from the wall
As long as you only plan on a system (shelves) on one side of the 4 foot "walkway", you'll be fine
You won't have room for systems on both sides of a 4 foot "walkway", as the minimum that is useful is 12 inches, and that only leaves 2 feet for "walk-in"
Depending on how wide your room is, you may need to place the door to the closet in the middle of the wall
Or perhaps more than one door
A 15 foot wide 4 foot deep walk-in closet could be a little much with one entrance on one "side" of the 15 foot dimension
Your effective hallway is only going to be 33 inches (with 15" shelves), that's a little tight