In the episode 'The Benders' (Season 1)

At the police station (or sheriff's office) which Dean goes to, to file a missing persons report after Sam is taken. When the officer looks through the files on the computer and it shows the personal details of both Dean and Sam, they both say 6'4" for height! It is obvious that Sam is 6'4" but Dean? I don't think so he is definately shorter than Sam.