Yes, you can paint wallpaper. It depends on the type of wallpaper and it depends on how well it is affixed to the wall. If your wallpaper is already peeling away from the wall in some areas, it is not a good idea to attempt painting it. Even if the wallpaper seems to be well in place, it may begin to peel once you begin to apply paint. If this occurs, you will need to remove the wallpaper and the glue behind it before painting.
Some types of wallpaper are made to be painted. In this case, you can usually paint the paper over and over again. If you are considering putting up wallpaper, a paint-able variety is a good choice. It makes for much simpler redecorating down the road.
If you plan to paint existing wallpaper and it appears as if it will take paint well, you should still use primer first. Always remember that water based primer works best with water based paint, and oil based primer is best with oil based paint.
If the paper has a strong print or pattern, take special care to completely cover patterned areas. Another tip is to add tint to the primer to bring the color closer to your paint color. This will help you avoid having to apply extra coats of paint in order to get even coverage. Prime the wall and let it dry thoroughly, usually up to twenty-four hours, before applying paint.
When primer is dry, look closely at the walls, especially in corners or where there are seams to make sure the wallpaper is firmly in place. If so, begin painting as you would any other surface.
If you can successfully paint your wallpaper, it will save you a lot of work. Most paper is a bear to remove completely, so painting wallpaper is definitely worth a try.