Believe it or not most women do! It just depends on how great the difference is.
However when you are getting fitted for a Bra you MUST always get fitted for the larger breast. Otherwise you will get spillage or the two boob look.
If there is a huge difference between the two then you can just get an insert for the smaller one to balance then out. I recommend if there is a big difference between the two the opt for a molded or semi soft cup bra that way it will disguise it.
I have answered other breast mysteries and common problems here at FAQ's