The Italian producers were so outraged by this film's story line that they forbid the director to shoot the film with a local cast and as such the roles played by Jill Clayburgh and Matthew Barry had to be changed to be Americans.
The film's "Luna" / "La Luna" title (translates from the Italian language as "Moon" / "The Moon") was derived from one of director Bernardo Bertolucci's earliest memories where he looked up to the face of his mother and then pivoted across to the moon and then saw the two images blend into one.
Theatrical feature film acting debut of Matthew Barry who had previously worked in television and off-Broadway. Barry has gone onto work as both a casting director and an actor. For this movie, Barry answered an advertisement in the show business trade journal "Variety" which had been placed by director Bernardo Bertolucci's casting agent for the role of the son in this film. Barry was selected as one of ten finalists from several dozen youthful aspirants to be interviewed by Bertolucci. After Barry's first reading of a scene, the competition was narrowed down to three contestants. Barry went screen tested in the semi-finals with actress Jill Clayburgh, and, after a second test, won the role.
Due to delays in filming Luna (1979), actress Jill Clayburgh missed attending a number of awards ceremonies for which she had been nominated for An Unmarried Woman (1978) whilst dubbing sessions for Luna (1979) had to be postponed until Clayburgh had finished work on Starting Over (1979).
The picture was controversial for examining an incestuous relationship between a mother and her son. Incest had also been a story element in director Bernardo Bertolucci's earlier film, Before the Revolution (1964).
To prepare for her lead role in this film, actress Jill Clayburgh studied opera singing under an Italian opera soprano as well as taking a course in Italian language but most of the film ended up being in English and only a small part of the film ended up being in Italian.