Sofia Coppola has revealed that Paris Hilton was not as she expected when they worked together, describing her as "cool".

The hotel heiress spent a day on the set of Sofia's new film The Bling Ring in a cameo role, and also allowed filming to take part in her home.

The Oscar-nominated filmmaker told Red: "Actually, I was impressed [with Paris Hilton]. She is more self-aware than you would expect. She was very helpful in making the movie, and aware yet relaxed about her image."

Sofia, who graced the front cover of the magazine's July issue, enjoyed getting a taste of the Paris lifestyle.

"I wanted to show what it is really like to be in Paris Hilton's closet - the thrill of entering it. It's like a candy store," she recalled.

"It was pretty impressive. I could not believe the amount of clothes. But Paris was cool," she added.

The film, which stars Emma Watson and Leslie Mann amongst others, is based on a group of teenagers who burgled the Hollywood homes of celebrities. Sofia admitted she was taken aback by the present-day teenage culture.

"I talked to my friend's 17-year-old daughter about the slang that teenagers use, and this lovely young lady explained that all her friends call one another 'b*****s, s***s and w****s," she said.

"I also went to clubs in LA with all the girls dressed up in miniskirts and sky-high shoes. That was pretty exotic. Everyone was texting, taking pictures, and I tried to put as much of that in the film as possible. It was almost sci-fi, this idea that living does not count unless you are documenting it. All those things interest me and say so much about our culture, and what is emphasised as important."