The TV presenter, who has hosted the show for six years, claimed that he could no longer listen to tracks by certain artists because he'd heard them too many times on the road with the ITV1 talent show.
"You do think, 'I can't possibly listen to these songs again'," O'Leary said. "You do get sick of hearing the same thing. There's Adele and Etta James's 'At Last' which stand out for me."
Last year, Gary Barlow confessed that he had told Adele he was bored of her songs because he'd heard so many covers while filming the ITV1 talent show.
Commenting on suggestions that the British public may have fallen out of love with the fame and celebrity of The X Factor following the London 2012 Olympics, O'Leary said: "That's the one I get frustrated about. To do well on the X Factor, you need to do a lot of work, especially if you want to reach the latter stages.
"What people see on a Saturday night is a such a small part, you can't possibly capture it. Plus, these people have been working for years before the show. There are very few overnight success stories."
O'Leary also downplayed any suggestions that his dance moves would be back during the opening sequences of the Live Shows, joking: "This is my sixth year, and I think what comes out of my mouth is better than my feet."
Commenting on rumours that Simon Cowell may be back on the show as a 'Voice of God' via Skype during the Live Shows, O'Leary laughed: "We all know he's probably here now watching what we're saying.
"What would he do? Interrupt me when I'm speaking and say, 'No Dermot, that's wrong'. I wouldn't like that."
The X Factor series nine launches on Saturday, August 18 at 8pm on ITV1.
Watch Johnny Robinson singing 'At Last' on the 2011 series of X Factor:
[X Factor series 9 Press Launch - Photo Gallery]
Copyright: WENN Daniel Deme