Talk about a power date!

Paris Hilton and Nicole Richie hit the Los Angeles opening of Joel and Benji Madden's first DCMA Collective clothing store on Friday.

Joel told Usmagazine.com that "it's not the first time we have all hung out.

"We have obviously known Paris for a long time, and [Nicole and Paris] have known each other for a long time, so it's nothing new," he added.

Benji and Paris made their romance public late last month. Nicole and Joel welcomed their first daughter, Harlow, in January.

Paris told Us that the four of them get together often, but "[Nicole and Joel] really don't go out, so we mostly hang out at her mom's house with the baby and watch movies and cook."

Paris couldn't stop raving about the store opening, which attracted The Hills' Audrina Patridge, Pete Wentz and Nicky Hilton and her beau David Katzenberg.

"They are really cute," Paris told Us of the DCMA collection. "They work with some of the most amazing graffiti artists to make these really cool T-shirts that no one really has."

Joel said they named their clothing line DCMA because "we are from a small town outside Maryland, and we used to go to punk rock shows. This just represents where I'm from: Washington DC and Maryland."