Research has found that although nightmares are no more common, they are now more often about bad stories in the news than scary creatures.
Sleep expert Dylan Glover, who took part in the research, told CBBC Newsround Online that this is because children have more access to the news through TV and the internet.
He said: "Parents are encouraging their children to watch the news more."
Recent high profile stories that have been giving you nightmares include the September 11 terrorist attacks, the murders of Holly Wells and Jessica Chapman and the Milly Dowler case.
He offered advice for children who were frightened by bad news.