Glen Mazzara discussed the relationship between his show and the source material.
"The comic book, and I've said it before, is a treasure trove," he told Collider. "It's a grab bag.
"We certainly have characters and storylines that we really want to do - but to get there in a TV series, you have to take your time. Sometimes you can't get right to it.
"They're two different mediums. So we make it our own and really own the material.
"I like to think of it as an alternate universe."
Mazzara also promised more deaths in the "hard-hitting" third season.
The Walking Dead is based on the original comic series by Robert Kirkman, who also serves as an executive producer on the show.
The Walking Dead returns to AMC in the US on October 14. In the UK, the series will air on FX later this year.