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)
Continuity mistake: In one shot while Luke is being trained on Dagobah, look at R2 when Yoda says, "Anger, fear, aggression, the dark side of the force are they." The little projection nozzle that sticks out of R2's head is on the left side of the red light (it's on the right side for the rest of the movie).