The choice to shoot the film in Hong Kong was inspired by the classic film Casablanca. Indeed, director Paul McGuigan explains that in the thirties and forties, Casablanca was a den for scoundrels and the perfect place to hide as everyone could go there. To the makers of the film, Hong Kong was the 2000's equivalent to Casablanca.
Director Paul McGuigan tried to limit the use of digital effects as much as possible, recalling the great directors who didn't have such means available to them yet made up for them with their imagination. In fact the only scenes in which green screens were used were the car chases, as Hong Kong traffic is very heavy.
The idea of a government agency controlling people with special abilities for military and/or intelligence uses is in fact inspired by real-life experiments of the US government, particularly the long-running Stargate Project.
In order to deal with the constant bustle of Hong Kong, director Paul McGuigan and the crew decided to shoot the film "guerilla-style", with the cameras hidden in vans, filming through small holes, and the actors doing their scenes in one take on the streets.
The different type of psychics in the film are Movers (who can move objects with their mind), Pushers (who can control other peoples' thoughts), Watchers (who can see the future), Bleeders (who emit high-pitched screams that can burst blood vessels), Sniffs (who can track people), Shifters (who can temporarily change what an object looks like to others), Wipers (who can wipe memory), Shadows (who can cloak themselves and others around them from detection) and Stitchers (who can heal or unheal people).
Director Paul McGuigan was much more interested in the character element of the picture than in its action element, stating that though it was an action movie, the characters were very developed, much more so than in most such genre films.
The subject of the film piqued director Paul McGuigan's interest and led him to find out all that he could about it on the Internet, some of which he found quite incredible, notably in the experiments conducted during the Cold War by both the Soviets and the Americans.
In Spanish (at least in Chile), the movie was renamed as "Heroes" at the cinemas, which led to confusion to moviegoers who were expecting some relation with Heroes, the TV series. Both the movie and the series tell the story of a group of people with super-powers being chased by a secret organization.