Robbie Buck will replace Adam Spencer as breakfast presenter for 702 ABC Sydney, after two years hosting afternoon programs for Radio National.

Spencer, who announced he was leaving ABC Radio in May, has not revealed his plans after he finishes with the broadcaster on December 6.

Buck for Breakfast: 702 ABC Sydney's new breakfast presenter, Robbie Buck. Credit:ABC

Buck said he was both "thrilled" and "terrified" to be taking over the role in January 2014, admitting he thought it was unlikely he would score the job.

"It has come out of the blue. There are a lot of people out there who would be good at it. And while I'm chuffed to be getting it, I didn't think my name would be at the top of the list."