Peek-a-boo it's Paris: Ms Hilton WILL go to the ball

So it came as a surprise to see her out on the town in disguise.

But not even a mask was enough to hide the heiress, as her distinctive blonde locks and long legs gave her away.

Having a ball: Paris Hilton at the Masquerade party in Los Angeles on Sunday

Paris was hosting a masquerade ball at the Kress in Hollywood to celebrate her
upcoming reality show, "My New BFF."

Not wanting to waste a photo opportunity though, the mask didn't stay on very long.

Paris opted for a vampish look in black prom-dress, torn fishnet tights and platform shoes.

Masquerading: Paris with her sister Nicky

Accompanying the socialite were sister Nikki and boyfriend Benji Madden.

The couple have been dating since February and have publicly declared their deep love for each other.

In a recent interview on America's Sirius radio, Benji said: "We have known each other for a long time, and I've always known the real Paris. I always knew that she was like...wife material or serious girlfriend material.

Paris with boyfriend Benji Madden

"You just want to get on top of a mountain and go, I'm in love! But your fans would probably make fun of you."

When asked if he would consider marrying Paris, he replied: "Nothing would make me happier. Wow, alright. Ok. I'm not gonna bet against you on that. We'll see. I'm very, very happy right now."

Paris has been engaged twice before - to American model Jason Shaw and Greek shipping heir Paris Latsis, while Benji ended his engagement to Australian singer/actress Sophie Monk just weeks before he started dating the hotel heiress.