Jim Sheridan said in interview that the character of Frankie, the dead son, was based on his real-life brother, also named Frankie.
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. After not finding the right girl to play Christy, he auditioned Sarah for the part of Christy and she turned out to be right.
Jim Sheridan wanted a 12 or 13 year old girl to play Christy, but Sarah Bolger was so impressive that she won the part despite being only 10.
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".