Continuity mistake: Just before Leia gives the order to evacuate and leaves the control room on Hoth, C3PO can be seen in the background with his hands over his head. The shot changes to a closeup of him, and his hands are now down at his waist.
Continuity mistake: When Yoda and R2-D2 are engaged in a tug-of-war over the little flashlight, Yoda hits him several times with his walking stick. When Artoo lets go, the stick is pointing upwards as Yoda hits him one last time, but in the next shot, Yoda is using it as a walking stick again and it is pointing downwards.
Continuity mistake: Widescreen version: After Vader chokes Captain Needa, he talks to Admiral Piett. The distance between Piett and the officer next to him differs between shots, depending on the camera angle. (01:10:55)
Continuity mistake: After R2-D2 opens the door to the landing platform during the escape from Cloud City, the droid exits through the door. Some shots later, he is back inside. (01:43:55)
Continuity mistake: Leia and Han become annoyed with C3PO's chattering, and Leia turns him off. However, if you watch him in the background, you can see his body move as he breathes.
Continuity mistake: When Darth Vader and Admiral Piett are talking on board the Star Destroyer at the end of the movie, in the first shot, a man is standing behind Piett. In the next shot of Vader and Piett, a different man is standing behind Piett. Then, in the third shot of Vader and Piett, the first man is back. The design of the wall and window also differs. Widescreen version only. (01:57:05)
Continuity mistake: When Vader is about to tell Luke that he is his father, as Luke says, "He told me enough," he is holding onto one of the thin poles next to him. In the next shot, his hand is positioned lower down and clutching the other pole. Also, his head is in a different position, seen from the markings on one of the other poles. The position of his head and hand changes in the next shot as well. (01:46:35)
Continuity mistake: Widescreen version: When Luke and Vader are fighting in the carbon-freezing chamber, as Vader says, "Only your hatred can destroy me.", the hose hanging from the ceiling behind Luke is pointed straight down, but in the previous shot, it was bent. This has nothing to do with camera angles - watch the smoke coming from it, it changes direction as well. (01:40:40)