• by Mark Walsh  @markfwal, November 21, 2013

Online radio service Pandora on Thursday reported a 50% gain in revenue in its fiscal third quarter, with mobile advertising breaking $100 million for the first time in the period ending Oct. 31.

Pandora posted adjusted earnings of six cents a share on overall revenue of $181.6 million. Wall Street analysts, on average, were expecting Pandora to earn six cents a share on revenue of $175.6 million.

Pandora continues to monetize effectively across the board,” stated company CEO Brian McAndrews in the earnings release, highlighting the 58% growth in mobile advertising in the quarter. That rate was slightly below the 61% rate projected by JP Morgan analyst Doug Anmuth in a research note this week.

Advertising, which remains Pandora's main revenue stream, increased 36% to $144.3 million from a year ago. Subscription sales, while smaller, continued to grow at a faster clip, up 156% to $37.2 million.

Looking at usage, total U.S. listener hours climbed 17% to 4.18 billion hours from 3.56 billion a year ago. Pandora's share of total U.S. radio listening in October reached 8.06%, up from 6.61% a year ago. The vast majority of that activity now takes place on mobile devices rather than PCs.

Pandora announced third-quarter results on the same day streaming music rival Spotify was reported to have raised nearly $250 million in new venture funding that values the Swedish company at more than $4 billion. In addition to Spotify, Pandora is also contending with a major new competitor in Apple's iTunes Radio, launched in September.

JP Morgan's Anmuth suggested in his report that Pandora so far had weathered the arrival of iTunes Radio reasonably well, with both listener hours and its radio market share continued to grow steadily. However, the service’s active user base declined 2.6% from the prior month, indicating the Apple service may be having some initial impact.

For its fourth quarter ending Jan. 31, Pandora forecast adjusted earnings between two cents and fours cents a share on revenue in the range of $185 million to $190 million. That compares to analysts' average estimate of four cents a share in profit on revenue of $187.6 million.

Pandora's shares were down almost 3% in after-hours trading following the earnings announcement after closing Thursday at $29.68.