Goofs

When the deformed creature comes out from behind the wire gate and begins to walk over to Cybil and Rose, Cybil puts her left hand up onto her gun twice between shots, before beginning to shoot it.

When Christopher and Officer Gucci, who's wearing a blue tie and gray trench coat, come out of the building, the camera switches back and forth between Rose and Christopher. When it finally reveals officer Gucci in the background behind Christopher, he's wearing a different colored tie and trench coat.

When Chris meets the officers on the bridge, it is pouring rain, but if you look at the river/stream below, there is no disturbance to the water.

After Rose is stabbed, the knife is dropped. When it is seen again, it is close to her with the blade pointing in the direction she is facing. When it is seen again, it is pointing in the opposite direction. The next shot shows it farther away and shifted in angle.

Two cans of food are still on the floor before Anna finishes packing up her things at the hotel and she doesn't grab them. Once she slings her backpack onto her shoulder though, the cans are suddenly gone in the next shot. In the following shot after, one can of food is still on the floor.

Normally police offices don't call their precincts "base", unless it was an MP. Police officers usually call their precincts/bureaus through use of a series of precinct codes.

When Christopher asks about Sharon at the garage, the mechanic is working on a Dodge Magnum with a West Virginia license plate on the front of the car. West Virginia doesn't issue front license plates.

Actresses Zsuzsanna Cseh, Onika Ndukwe, and Nicole Ann St. Hill have their names spelled wrong in the credits as Zsuzzana Cseh, Onika Nduke, and Nicole-Ann St. Hill respectively.

The image of West Virginia on Cybil's arm patches is backwards.

As the miners are trying to break down the washroom door, the camera pans over the door frame from Rose's side to the miners' side. Just as it settles into its final position, you can see the sliding wall section they used to allow the camera to pan sliding back into position on the left of the door frame.

As the long-haired cult member is smothered by Alessa's barbed wire, the ladder that Sharon is supposed to be tied to is clearly visible and Sharon is not there.

The parallel dimension of Silent Hill must have an ability to keep batteries alive indefinitely for Rose to find a 1970s battery-operated flashlight that still works.

Lisa Garland (the Red Nurse) was Alessa's nurse back when she was burned alive in 1974. When Rose encounters her in the otherworld in present day, she appears to be the same age even though it has been 30 years. It's unclear if it's actually her though or if it's just a mental projection of the nurse by Alessa.

Agent Cybil Bennett uses a Surefire M6 Guardian flashlight that has a temporary tailswitch with a twist-on constant switch, but in the movie you can clearly hear the typical click of a click-on switch.

When Christopher breaks into the Brahams archives offices at about 0:59:45, the clearly visible orange anodized end caps and typical wiring on the fluorescent tubes identify them as Kino-Flo lights, a specialist type manufactured solely for the film industry. The arrangement is quite different to a conventional domestic lighting system. Orange end-caps indicate a tungsten-balanced tube; blue would be daylight.

The gas station Rose stopped at and passes at the end has gas listed as per Canadian liters instead of the American gallons.

The film is supposed to take place in West Virginia, yet all the local townspeople have distinguishable Canadian accents - the movie's primary filming location.

The cultists in Silent Hill have been trapped in the alternate reality for 30 years after Alessa was burned alive. Given that the water supply likely dried up years prior, and crops obviously can't be grown in the hellish other-world, where did they get food and water from to survive all those years?

At the 30 minute mark when Chris meets Officer Thomas Gucci at the bridge, there was never any mention of Chris's daughter. Yet mistakenly Officer Gucci reassures Chris they will find his wife AND daughter.

Cybil not following Rose into the elevator and instead staying behind to fend off the cultists was a stupid move given the situation. The cultists would have had no way to stop the elevator from descending once the door was closed, so all Cybil had to do was quickly jump in with her. Yes, staying behind bought Sharon some time to live, since the cultists spent their time burning her alive first before Sharon, but there's no way she could have known that at the time.