Continuity mistake: When one of the stormtroopers unties Han Solo before he is put into the carbonite, watch his wardrobe - he has a disappearing / reappearing jacket on. This is fixed to an extent on the DVD - the jacket is now lightened to almost match his shirt, but it's still shiny like leather. (01:32:05)
Continuity mistake: When the AT-AT that Luke destroyed with a thermal detonator falls over, Luke is nowhere to be seen, even though he should be visible, judging from his position in the previous shot. (As noted in another mistake, the AT-AT is suddenly further away from him after he falls to the ground, but he is still to close to be out of shot when it falls over.). (00:31:45)
Continuity mistake: Near the end of the film, when the Millennium Falcon is trying to get away from Vader, there's the scene in which Vader asks the admiral if he disabled the hyperdrive on the Falcon. This scene is backwards, as you can tell by the insignia on the admiral's chest. Normally it should be on the left side of the chest, but in this scene, it is on the right side of his chest.
Continuity mistake: Widescreen version: When Leia, Han, Chewbacca and C-3PO are first walking through Cloud City, as Han says to Lando, "You sound like a businessman", Chewbacca is walking behind Leia. In the next shot, he is ahead of her, and then seems to walk to the side to wait for her. In the following shot, he is behind her again. (01:18:45)
Continuity mistake: When Vader and Luke are duelling on the catwalk over the chasm, Luke lies on his back after he falls. In the first shot, he is lying in front of the steps leading to the round part of the platform, but when he rolls sideways a few seconds later, he is lying on that part of the platform.
Continuity mistake: After Luke first sees Boba Fett in Cloud City, he begins to walk away from the corner he is hiding behind. In the next shot, he is closer to the corner than in the previous shot. This has nothing to do with camera angles - notice the distance between him and the wall to his left. Also, his right arm is in a different position. (01:34:55)