Jack McElhone (Frankie) is not deaf but worked with a speech coach so that his one spoken line would sound correct.
The song that plays while Lizzie (Emily Mortimer) is sitting on a bench crying after a fruitless attempt to find a "daddy" for Frankie, is written by one of the most famous contemporary Estonian composer - Arvo Pärt.
This attracted a 15 minute standing ovation when it debuted at the Cannes Film Festival.
"Dear Frankie" was filmed on location in Scotland, at Buchanan Street Stamps, Glasgow, Strathclyde, Scotland; Film City Glasgow, Govan, Glasgow, Strathclyde, Scotland; Glasgow, Strathclyde, Scotland; and Greenock, Inverclyde, Scotland.