Scarlett Johansson said she nearly crashed her car when she saw her "brontosaurus-sized" boobs on a billboard.
The Lost in Translation actress slammed on the brakes when confronted with a giant advert of herself in Hollywood, according to the Daily Record.
And the 20-year-old hinted that the picture of her chest had been digitally altered to promote new movie, The Island.
She said: "I was driving through Los Angeles and I look up and see the biggest photo of me I have ever seen in my life on a massive ad space.
"I screamed and slammed on the brakes. I couldn't believe it.
"It's very strange to see my cleavage the size of a brontosaurus. My breasts were huge.
"I had long hair and my goodness, I couldn't get past the cleavage."
The Island, in which Scarlett stars alongside Ewan McGregor, has flopped at the US box office.
The pair are portrayed in a nightmare world where human clones are bred to provide spare body parts.
But Scarlett revealed she enjoyed her kissing scenes with the Star Wars hunk.
She said: "I get paid to make out with Ewan McGregor and roll around in bed all day. It's a hard job but somebody has to do it."
