The music mogul and the actress were said to have dated between 2008 and 2012, and it's been claimed Diddy, 45, wishes he took their union further.
A source for Us Weekly claims to have overheard Diddy describing Cameron, 42, as the "sexiest girl in the world".
The insider explained: "He was at dinner and the subject turned to Cameron dating [her current boyfriend] Benji Madden. 'If I could turn back time, things would be different!'"
The pair are said to have first met at the Oscars in 2008, and they were pictured together on a number of occasions in the following years - although their respective representatives always denied they were dating.
Here is the former couple getting all loved up back in 2008:
(Cameron Diaz and P Diddy. Getty Images)
One noticeable difference between the pair is their attitudes towards family.
Diddy has five children from different relationships, while Cameron says not having kids has made her life easier.
Earlier this year, she told Esquire: "To have lives besides your own that you are responsible for, I didn't take that on, that did make things easier for me.
"A baby, that's all day, every day for 18 years. Not having a baby might really make things easier, but that doesn't make it an easy decision.
"I like protecting people, but I was never drawn to being a mother. I have it much easier than any of them. That's just what it is. Doesn't mean life isn't sometimes hard."