Adam Lambert has thanked Britney Spears after attending her Las Vegas residency show.

The vocal powerhouse was in the audience at Spears' Piece of Me opening gig at Planet Hollywood on December 27 and it seems a good night was had by all.

The pop princess reached out to Lambert on Twitter, saying:

"@adamlambert Thanks for coming to #PieceOfMe last night!!! Means a lot to me :)."

Lambert replied: "I had so much fun!! Thank you for a great show!"

The 'Trespassing' singer meanwhile was spotted dancing with Miley Cyrus at the concert, which is due to run for two years.

They weren't the only stars in attendance at the opening show, however.

The likes of Katy Perry, Selena Gomez and Sia all made the trip to Vegas to check out Spears in action as she ran through her hits.