Continuity mistake: In season 2, episode 5, Jin and Mr. Eko are searching for Michael. Jin gets attacked by a boar and rolls down a hill to find the corpse of Goodwin. In this scene they are in the middle of the jungle. Two epiosdes later ("The Other 48 Days"), when Ana-Lucia confronts Goodwin they are on top of a mountain without trees surrounding them. This is confirmed in Juliets flashbacks in later seasons when Ben takes her to see Goodwins body.
Continuity mistake: After picking up Eddy the hitchhiker, John and his passenger can be seen driving through a compound. As they drive through the compound, a passenger can be seen in John's pick-up truck. The scene just before they arrive at the sweat lodge, there is no passenger. Once they arrive at the sweat lodge, a passenger exits the pick-up truck. (00:16:25)
Continuity mistake: As Locke stabs Jack's neck in their final battle, the wound is visible, above the neck line of his shirt. Once the rain stops and Jack speaks of his plan and kisses Kate, the wound is missing for the entire scene. The wound reappears on his neck during Jack's scene with Hurley and Ben at the cave opening. During the final sequence as Jack lies down and closes his eyes, the wound is visible in most shots, but in the final two wide shots, the dry blood make-up appears to be coming off and once again there is no neck wound.
Continuity mistake: At the end, when we see Ben lighting a candle with a matchstick in the cathedral during the entering of Eloise, he puts out the matchstick so we see that the flame is gone. In the next shot, the flame is back and Ben is doing exactly the same thing, but we see it from another view.
Continuity mistake: Ses. 5, ep. 5, "This Place is Death". When Daniel is telling Charlotte that he has a plan, and explains, "When we were back at the hatch, I talked to Desmond", he places his left hand on top of his right, holding Charlotte's hand between them (seen at bottom of the screen). When the angle changes to a shot above his shoulder, his left hand is suddenly back under Charlotte's head, with no time to move between shots. (00:32:50)
Continuity mistake: In the very beginning of the pilot episode, Jack runs out of the jungle. He looks around and hears distant screams. While he is looking around, you can see through the bushes that there is nothing but beach on the other side. But when he turns around, the entire beach just on the other side of that bush is filled with wreckage. The wreckage would have been visible from the other side of the bush had it been there.