When the film was originally released, It became both the highest-grossing Korean horror film of all time and the first one to be screened in American theatres.
The movie is inspired by a famous Korean folktale, called "Janghwa Heungryeonjeon" which although has been adapted to film several times, this one specifically is not a remake of any of them and is its own original project.
Director Kim Jee-woon originally wanted Jun Ji-hyun to play Su-mi, however Jun refused the role of Su-mi because she thought the script was too scary. Ironically, her next project was another horror film, 4 inyong shiktak (2003), which was translated into English as "The Uninvited." Coincidentally, "The Uninvited" is the title of the American remake of this film.
In the original story, the sisters' names are Janghwa and Hongryeon (Rose Flower and Red Lotus). In the movie, they are Su-mi and Su-yeon (still meaning Rose and Lotus).
Lim Soo-jung, who played Su-mi, originally auditioned for the role of Su-yeon. Ironically enough, the same thing would happen in the remake Presencias extrañas (2009) where Emily Browning originally auditioned for the role of her sister Alex before being cast as Anna.