Other: In the scene where Costigan drags a handcuffed Sullivan into the elevator, Costigan slams Sullivan against the wall and his left arm is visible and not in handcuffs.

Continuity: When Costigan is with Madolyn in her office, the tissues in the tissue box change consistently between shots.

Continuity: At Billy's mother's funeral, the signature of Frank Costello on the flowers changes between shots.

Continuity: When Ellerby attacks the guy for not installing the cameras in the right place, he knocks off a map from the board. A second later Ellerby is still going after him, and the map is fixed.

Revealing: ***SPOILER*** When Costello is killed, a blood-pack is noticeable under his shirt.

Continuity: In the scene after Queenan dies, when Sullivan picks up his phone to contact Costigan, he presses the "talk" button and a smudge of blood is left. In subsequent shots, there's no trace of blood on the "talk" button.

Revealing: When Costello's hooligans drive away from 344 Wash after the shoot-out, Queenan's body on the ground is quite obviously a dummy.

Audio problem: When Matt Damon answers Costello's phone the girl asks "where the hell are you?" but her mouth says "where the F*** are you.

Continuity: In the restaurant, after Costigan says "The Academy is over" he starts to bring the cigarette to his mouth but before he smokes, while the action, music and dialogue continues, the shot cuts to him already exhaling the smoke.

Visible crew/equipment: When Costello is looking at the dead corpses on the beach, two beams of light get reflected on his glasses.

Continuity: When young Sullivan is at Mass, a priest is swinging the smoking incense burning. In the next shot the smoke is gone, and he is away, arriving with the burner and repeating the previous movement.

Continuity: In the scene where Costello's bad guys are pulling up in the van to the building where Queenan and Costigan are talking, you can see the wet tire marks where the van stops before it gets there.

Continuity: The top layer on their dessert changes when Sullivan and Madolyn are in the restaurant. Between shots, the top piece changes back and forth between flat and curved.

Continuity: During the final shootout between the baddies and the cops, the pilot window of the grey GM is destroyed but appears perfect a second later.

Continuity: When Costello and French encounter the cops, the first shot shows the cops' car turning their lights on. In a new shot a second afterwards the lights on the middle and right side cars are out and they are turning them on again. On yet another new angle, the lights on the car on the left turn from off and on again in a split second.

Continuity: While Queenan is talking to Costello out on the street, watch the people behind him. First there's no one, then we have a shot of a woman and a huge line of kids passing next to her. Then back to Costello and the woman, who hasn't moved, is now miraculously visible behind him. To add to the mess, the kids have vanished.

Continuity: While Costigan is having coffee with Madolyn, a coffee cup suddenly appears in his hands close to his mouth, and the toothpick that was in his mouth a second ago vanishes.

Continuity: When Queenan is interviewing Costigan, the metal thing and the papers around it keep changing positions depending on the angle.

Continuity: When Sullivan is analysing the Providence corpses, the close-up shows both of his hands together, but on the wide shot one is near the corpse, and the other one close to his hip.

Continuity: When Sullivan and his pal are watching the golden dome building from a bench, from a back shot his friend has his head faced straight, but from the front shot it's sideways.