Jim Sheridan said in interview that the character of Frankie, the dead son, was based Frankie Sheridan, his late brother. The film is dedicated to this Frankie in closing credits.
During casting calls, director Jim Sheridan recalls that after a long day of auditions, he was very glad to have found Emma Bolger to play Ariel. He said that that little girl "told" him that he had to cast her sister Sarah Bolger as Christy. Sarah was only 10, and he had wanted Chirsty to be 12 or 13. After exhausting all other options, he auditioned Sarah for the part of Christy and she turned out to be so impressive that he didn't mind about her age.
The child actors (Sarah Bolger and Emma Bolger) called "cut" and "action" in every scene. This was decided by the director and the girls early during filming, so that it would make the acting easier for them.
The street fair scene was filmed on Parnell Street in Dublin, Ireland. The street was closed for three days for filming. A closed burger shop was used as a green room for cold extras.
Ewan McGregor and Kate Winslet were originally approach to play Johnny and Sarah at the film's early stages of production when it was entitled "East of Harlem".