The Charlie's Angels star, 39, was spotted on the beach in Hawaii over the holidays looking rather shapely, prompting rumours she's gone under the knife.
The actress is said to have had implants to boost her chest by a cup size, according to the National Enquirer.
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Plastic surgeon Dr Anthony Youn, who has not treated the star, told the publication: 'I believe she has had a breast augmentation using relatively small silicone implants.'
'Since swelling can take severely weeks to settle down, I suspect she had the surgery at least two to three weeks ago.'
Cameron has previously said she'd prefer a more curvy figure, telling Marie Claire in 2009: 'I'd love to be more voluptuous. It's just not my body type."
The star, who had her nose fixed in 2006 after breaking it four times, said in 2010 that she would rule out more surgery.
Cameron Diaz in January 2012 (left) and in January 2011 (right)