Justin Bieber celebrates turning 18 with a grown-up shoot in GQ magazine.

The Biebs has also learned to be disciplined when talking with the media. He rarely says much about his famous girlfriend Selena Gomez, 19, who's been spotted with him on the red carpet, vacationing in exotic locales, visiting his hometown in Ontario, Canada, and dining out at their favorite restaurant, IHOP. Unfortunately, Bieber remains mum on her in the interview. He did, however, talk about another brunette beauty — Kim Kardashian, who he became friends with after posing alongside her for an Elle photo shoot in 2010. "People say she doesn't do anything; she actually does do stuff," Bieber says in defense of the much-maligned reality star. "She works hard." Bieber's had his own share of haters, and he seems to know it. "I mean, I keep my guard up a lot, because you know, you can't trust anyone in this business," he notes. "That's what's sad. You can't trust anybody. I learned the hard way."