Jennifer Connelly appears as Cillian Murphy's mother, but their actual age difference is only 6 years.
The scene of Jenia and Ivan walking across the frozen lake at night was filmed on an actual frozen lake and at night. Director Claudia Llosa had great difficulty getting the go-ahead for the night time shoot on the lake because it was deemed too dangerous.
When the film was screened at the Berlin Film Festival, it included intimate scenes of Cillian Murphy and Mélanie Laurent, but they were excluded from the theatrical version. The director thought it better to delete them. Murphy watched the uncut version with his wife at the Berlin Film Festival.
Temperatures dropped as low as minus 30 during the winter shoot in Canada.