Whatcha smokin' there, Mischa?

Actress Mischa Barton takes a puff off what appears to be a homemade 'cigarette' Wednesday, and Breaking Celebrity News has the pics.

The former O.C. starlet, 24, was photographed aboard a yacht with her boyfriend Lee Tinklin (also known as DJ Ali Love)  and some pals in St. Tropez, France.

Last summer, Barton - who's long been rumored to have battled substance abuse problems - was placed on psychiatric hold at the Cedars-Sinai Medical Center after police were called to her L.A. home to deal with a so-called "medical issue."