When it comes to decoying deer while bowhunting, distance is a major consideration on two fronts.
The farther away a deer is when it first sees the decoy, the better the odds are that it will come all of the way in to the decoy. Field edges, fence lines, clearcuts, logging roads, power-line and gas-line right-of ways and natural openings in the timber are all good places for a decoy.
The other distance to factor into the equation, is how far from your stand you position the decoy. In most cases, I like the decoy to be standing 20- to 25 yards upwind from my treestand or ground blind. Most of the bucks, which respond to the decoy will circle in downwind of the decoy, which I suspect is the bucks attempt to get a whiff of the other deer. When they do, they will offer you an easy shot at close range.
Don't Use It In Dense Cover
If you can put it on a little rise where it is even more visible, so much the better. In heavy cover, where a buck is going to be right on top of the decoy before he can see it, a decoy tends to startle more deer than it attracts. I don't know why this is the case, but I've spooked enough bucks while attempting to decoy them in dense timber, that I no longer use a decoy when hunting the thick stuff.
Some bucks, however, don't follow the rules and don't bother to get downwind of the decoy. If you put the decoy too far away from your stand, a buck that hangs up short of the decoy is likely going to be out of range. Thus, I draw the line at 25 yards in most circumstances.
Skimpy Cover? Set It Farther Away
Occasionally, however, I have set the decoy farther away, sometimes up to 50 yards from my position. Most often, I do this when I am forced to hunt from a ground blind in skimpy cover.
Whitetail deer in general, and especially mature deer, are leery of ground blinds, which cannot be tucked into good cover. But if you can get them to focus on the decoy in the distance, they will often ignore the ground blind as they pass by on their way to the decoy.
Distance is just one of the factors which will determine your success when using a decoy, but it is a major consideration.