Is it possible to paint over existing wallpaper?
—Asheesh, Fremont, California
It's possible, but it's bad practice and we don't recommend it. First of all, the job can never be made to look good. Second, it's a sign of lazy workmanship. Third, painted wallpaper is a real bear to remove, so you'll make the job even tougher for yourself or someone else down the road. If the paper is unpainted now, a wallpaper steamer will make fairly short work of removal, then you can clean the wall with a solution of vinegar and water, then prep, prime, and paint as if it were a raw plaster wall.
Watch a pro painting contractor remove old, painted wallpaper: How to Strip Wallpaper