"It's bigger than what I can ever imagine. It's unexpected totally, so it's a surprise," Brown said in an interview Thursday.
It shouldn't be too much of a surprise for Brown. He not only nabbed the Billboard honor in 2006, he had a great '08, with solo hits like "With You" and "Forever" as well as successful collaborations, like the Jordin Sparks duet "No Air." Last month, he won three awards at the American Music Awards, including artist of the year.
But the 18-year-old Brown says he's still not used to all the accolades.
"I've had a good year but I still feel like a little insecure in those parts. I'm like, `There's little ol' me getting an award' - that's incredible," he said.
The artist's rankings are determined by album sales as well as digital downloads, radio airplay and Internet streams. The No. 2 artist was Lil Wayne, who had a huge year thanks to hits like "A Milli" and "Lollipop"; No. 3 on the list was Rihanna, whose hits included "Take A Bow" and "Disturbia," which was co-written by boyfriend Brown.
Billboard named Flo Rida's "Low" as the year's top song, followed by Leona Lewis "Bleeding Love," Alicia Keys' "No One," Lil Wayne's "Lollipop" and "Apologize" by Timbaland featuring OneRepublic. Brown had three songs in the top 10: "With You," "Forever" and "No Air" with Sparks.
The rest of the charts are available on Billboard.com.