A trip to the movies is a highlight of the school holidays for many kids, but a Perth cinema full of families had a shock when a trailer for a horror movie dubbed "this generation's The Exorcist" was shown.

A Peter Rabbit viewing turned into a horror show for Perth kids.

Perth woman Jane* told WAtoday she had taken her sister's children on an outing to Event Cinemas in Innaloo on the Anzac Day public holiday to see Peter Rabbit, a cuddly adaptation of Beatrix Potter's classic children's story starring Margot Robbie and Daisy Ridley.

Jane said the cinema was full of families including "at least 40 children" when the lights went down and the show began with a reel of adverts.

"Nothing to worry about there, but then the first trailer that was shown was for Hereditary, a horror movie that even I wouldn't go see," Jane said.