Continuity mistake: When one of the Storm Troopers unties 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.
Visible crew/equipment: Chewbacca enters the "junk" room to collect the remains of Threepio, and in the close-up scene of Threepio's head on the conveyor belt, you can see a reflection of the camera and several of the crew.
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.
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.
Continuity mistake: When Han is trying to keep Luke warm, his rank insignia badge alternates between being on the right and left side of his chest. The amount of snow on Han and Luke's clothes also changes repeatedly, especially Luke's.
Visible crew/equipment: When the Wampa (ice creature) kills Luke's Tauntaun, the end of the "glove" used as the Wampa's arm can be seen in the bottom left corner, as well as the arm of the crew member wearing it. Widescreen version only.
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.
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.
Continuity mistake: When the stormtroopers push Leia into the cell in Cloud City, she is wearing a completely different outfit from when she was taken captive.
Continuity mistake: When Luke is hanging upside down from the roof of the ice creature's cave, his legs are apart. But in the close-up of his feet, his legs are together.
Continuity mistake: When Luke is hanging upside down in the monster's cave he uses the Force to get his lightsaber. In the shot from Luke's POV it's about 3/4 buried in snow, but in the reverse it's only about 1/4 buried.