Internet radio site Pandora reported today that in December, 75 percent of its total listening hours came from mobile and other nontraditional devices.

In addition, the company reported that more than 125 million registered users have accessed Pandora on a smartphone or tablet, an about 1 of 3 U.S. smartphone users have listened to Pandora in the past month.

The company also reported that mobile and device revenue represents about 55 percent of its total ad revenue, and that its total mobile revenue brings in about a quarter of a billion dollars annually. According to Pandora, the company’s mobile ad revenue in 2012, was No. 2, second only to Google.