Break out the Kleenex... Cameron Diaz is back on the big-screen in the riveting, bittersweet emotional drama 'My Sister's Keeper,' featuring Abigail Breslin and Sofia Vassilieva, and she talks to our Kevin Frazier about what it was like playing a mom.

"I understand what it's like to love deeply," she tells Kevin. "I have nieces and nephews. I don't know what it's like to have my own child, but I know what it is to care about people."

In theaters June 26, 'My Sister's Keeper' finds Cameron as Sara, a mother who is devastated when her precious toddler daughter Kate (Sofia) comes down with a rare form of leukemia. Sara and her husband Brian (Jason Patric) conceive another child out of desperation, a daughter named Anna (Abigail), who is a perfect genetic match and will be able to save her sister's life. But the family's world is turned upside down with Anna decides, at age 11, to seek emancipation to avoid being forced to give her sister a kidney.

"Each one of them is just doing what they believe is the right thing," says Cameron of the film's characters. "What [my character] wants to do is save her child."

Watch ET for more with the stars of 'My Sister's Keeper.'

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