The 20-year-old star tweeted about the piece a few hours before the event.
"Hmmm .... What to wear... What to wear..... Hmmmm. Valentino ❤ you've never done me wrong!" she wrote.
According to Us Weekly the "Ashtrays and Heartbreaks" singer, who attended the event alone, flashed her engagement ring from Liam Hemsworth several times during the event.
Last month Maxim announced that Cyrus was voted number one on the magazine's 2013 "Hot 100 list."