The effect for the exploding head scene was accomplished by filling a latex head of the actor with dog food, leftover lunch, fake blood and rabbit livers, and shooting it from behind with a 12-gauge shotgun.
David Cronenberg once called this the most frustrating film he'd ever made. The film was rushed through production - filming had to begin without a finished script and end within roughly two months so the financing would qualify as a tax write-off, forcing Cronenberg to write and shoot at the same time. Cronenberg also cited difficulty with and antagonism between the leads, particularly Patrick McGoohan and Jennifer O'Neill.
William S. Burroughs' 1959 novel 'Naked Lunch' contains a chapter concerning "Senders", a hostile organization of telepaths bent on world domination, a clear literary inspiration for this film. Cronenberg would later direct a film version of Naked Lunch (1991).
A very early treatment from 1976, entitled "Telepathy 2000" takes place in the future, begins with the protagonist (who is named Harley Quinn) telepathically raping a woman in a subway, and was set as a spy movie. In this version, a company called Cytodyne Amalgamate was breeding evil Scanners to take over the world and the U.S. Government was employing good Scanners to stop them.
The crash scene in the record store prominently features a float hanging from the ceiling for the RSO (Robert Stigwood Organization) record label, who paid for this placement. By the time the film was released, RSO had gone out of business.
In February 2007, Darren Lynn Bousman was announced as director of a remake of the film, to be released by The Weinstein Company and Dimension Films. David S. Goyer was assigned to script the film. The film was planned for an October 17, 2008, release, but the date came and went without further announcements, and all the parties involved have since moved on to other projects. In an interview with Bousman in 2013, he recalled that he would not make the film without David Cronenberg's blessing, which was not granted.
In an interview with Film Comment, Stephen Lack recalled feeling under-the-gun during one of his first scenes on set. "There we were, the first day of Scanners and they had me get into this 18-wheel truck with four gearshift levers and have me drive into the shot. It was horrifying. I never drove such a thing and I was pretty disoriented," he explained. "We were set up on a feeder road to the highway, and all the camera crew and staff were there, and some car on the highway slowed down to gawk-and a truck on the highway rammed them from behind. There was a death and sirens, and the whole crew jumped over the storm fence to help out. I was given a slight reprieve of an hour to figure out the gears."
The drug ephemerol bears an eerie similarity to the real-life scandal in the late 1950s as women who had taken thalidomide during pregnancy (marketed as relief for morning sickness) began to give birth to children suffering phocomelia or other physical deformities.
The life magazine that Revok shows Vale during their discussion at the end of the movie is from July 22, 1946. The prop is the actual issue. Revok opens it to page 38-39, but the close up is of page 48-49. The Ephemerol add is pasted over an ad for Bendix Radios on page 49.
This was the nearest thing to a conventional science fiction thriller David Cronenberg had made up to that point, lacking the sexual content of Shivers (1975), Rabid (1977), or The Brood (1979). It was also his most profitable film until The Fly (1986) six years later.
The trivia item below may give away important plot points.
Production stills exist of shots in the final duel between Cameron and Revok, where the top of Cameron's head explodes, sending sparks into the air. Apparently this climax was filmed but David Cronenberg chose to omit it from the final print.