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).
Continuity mistake: After Leia, Han and Chewbacca walk down the stairs in the carbon-freezing chamber, as the shot ends, Han is turning towards a stormtrooper behind him. In the next shot, he is turned in a different direction, and Leia's head is facing another way. The position and existence of some of the people around them changes between the two shots as well. (01:31:10)
Continuity mistake: When Han and Leia kiss in the Millennium Falcon, Leia's arms are around Han's head in the wideshot, but not in the close-up. (00:49:55)
Continuity mistake: When Vader is seen in Cloud City, Lando says, "I had no choice, they arrived right before you did" and two of the stormtroopers on the lowest step are standing about a metre apart. In the following close-up of Lando, they are standing so close together that their ankles are touching. This can only be seen in the widescreen version. (01:25:05)
Continuity mistake: When a blast rocks the command centre during the battle on Hoth, C-3PO is thrown backwards into Han's arms. As the wideshot leaves, Threepio is leaning backwards, supported by Han, but in the next shot, both of them standing upright in a normal way. Toryn Farr, the woman sitting behind them, has changed position as well. (00:30:40)