Continuity mistake: When Leia is briefing the Rebel pilots, some of the men behind her change position between shots.
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: After Vader cuts through the poles at the end of the duel, the burn marks keep changing size and appearance between shots.
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: When Lando is talking to Han and Leia in the cell in Cloud City, Leia says, "And we're the bait." As the shot ends, her hand is on the nape of Han's neck, but in the next shot, her hand is on his back. (01:29:15)
Continuity mistake: When Han first walks into the command center on Hoth, there's a shot of Leia looking at him. The shot has been flipped. This can be seen, for example, from that the men on either side of her have switched sides. (00:04:50)
Visible crew/equipment: A few seconds after Slave 1 (Boba Fett's ship) takes off there's a close-up of R2 and the camera and two crew members are reflected in his head. (01:43:15)
Revealing mistake: After Chewbacca pulls R2-D2 away from the power socket, he runs away, and you can see white rubber soles under his feet. (01:43:15)
Revealing mistake: In Cloud City, Lando, Leia and Chewbacca are running to the Millennium Falcon, and when then they run into a door after Leia shoots a stormtrooper, a white rubber sole can be seen under one of Chewie's feet. (01:42:40)
Other mistake: In the original version, when the Rebel Transport ship leaves Hoth before the ion cannon is fired, an X-wing flies past it, and you can see the transport ship through one of its wings. This has been fixed in the Special Edition.
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)
Revealing mistake: After the headless AT-AT begins to fall over, watch its back leg on the right side of the screen. You can see a broomstick being pushed up from under the set. It raises that foot up in order to ensure that the AT-AT falls to the left side of the screen. (00:33:00)
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).