Some people don't think so, but I say yes. I've seen lots of different paranormal investigation shows and read a lot of real books about true hauntings, so I believe in it. Think about it like this: what happens when you die? What if you don't want to go to heaven or to hell? What if you want to stay on Earth?
Depends on yer beliefs. And also on what is happening to make you think there's a ghost. Haunting work on different levels. Such as a ghost is usually just an image,not really causing harm. Just being seen. As while a poltergeist usually moves things and or tries to make communication, in some manner. either way yes they are real