Continuity mistake: In the first scene when Rigel is crouching, taking pictures of the werewolves, he is holding the camera in his right hand just as he is about to jump down. However, when he is jumping, the camera angle changes and it can be seen that he is no longer holding a camera in his right hand.
Revealing mistake: After Selene jumps off the building at the beginning and lands, there is a very large upwards pull (that stays in place until the camera cuts away) in her cape near her head that is in fact the drop wire running under her cape to the harness on her back (although the wire has been edited out).
Audio problem: At the beginning, when Selene is hunting the Lycan though the subway tunnels, she is pressed against a wall, and she starts to look around the corner. Then suddenly a subway train passes by. Shouldn't we have been able to hear it?
Continuity mistake: During the fight scene between the two Lycans, it shows a shot of Taylor (short Lycan) receiving a cut across the left side of his chest, but when it shows him in his human form it is on his right.
Revealing mistake: As Lucien reprimands the Lycans for their pit fights, of the two Lycans who were just fighting and were naked during that fight, on the taller one the top seam of his underwear/pants is visible.
Audio problem: Near the beginning of the movie, while Selene is looking at the CCTV video from outside the subway station, Kraven enters the room and talks to her. Throughout their conversation, the sound quality of his voice changes as he walks away from where the mic is located (by Selene).
Continuity mistake: Selene is in Michael's apartment looking through photos, you can see the door to the apartment fully open in the background. When the phone rings, and we see Michael walking towards his apartment, the door is only partially open.
Revealing mistake: When Selene is firing her guns in the floor making a circle of holes so that the floor collapse, you can see in some shots the angle of her guns are pointing all kinds of directions. Instead of making a perfect circle the holes would be spread around the floor and the bottom of the walls in the hallway.
Continuity mistake: When Lucian goes flying over Selene's car, in the overhead shot we see that the road below him has large parts with visible concrete because there are no paving stones. But in the next shot, a close-up of Lucian landing on his feet, the road is fully paved with paving stones.
Other mistake: When Selene's car plunges into the Danube, her car hit the bottom of the river on it's side (the passenger's side). When the camera closes up to the window of the car, you can see water flowing in from the roof of the car (as a result from the holes created by Lucian). It should flow (or at least accumulate) towards Michael's direction because of gravity but it did not.