Marissa Cooper returns!

Mischa Barton was all smiles lounging in a beach chair in Miami, Fla. on Tuesday.

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And why not? The sometimes-troubled star, 25, looked the slimmest she has since her days as the buzzed-about star of The OC. Clad in a skimpy two-piece bikini, Barton grinned from ear-to-ear behind her sunglasses, showing off taut abs and more.

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Barton, whose weight has fluctuated since her heyday, recently wrapped filming her role as the beautiful love interest in the flick The Misadventures of Ben Blanks.

She checked into a psychiatric hospital in 2009, and opened up about her battle with depression in fall 2010.

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Tell Us: How do you think Barton looks these days?

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