It's a bit of both. Many visitors who go to Pripyat report strange feelings and some claim to have seen things. However, it could be the power of suggestion. The history of the place, with its sudden evacuation and the lingering signs of a once - busy life, makes it a prime location for the mind to create ghostly stories. But there's no scientific evidence to prove the existence of real ghosts.
Some of the Pripyat ghost stories might be based on real experiences, at least in the sense of the atmosphere creating a sense of unease. The abandoned city has a very eerie and desolate feel. People's minds can play tricks on them in such an environment, making them think they see things that aren't there. But as for actual ghosts, it's more likely superstition.