NEW YORK -- A year ago Facebook was just testing the waters of mobile advertising, causing plenty of headaches for investors ahead of its massive initial public offering.

It has since eased those worries.

On Wednesday the world's biggest social networking company said nearly a third of its advertising revenue came from mobile in the first three months of the year, helping to push total revenue up 38 per cent to surpass Wall Street's expectations.

Facebook Inc. said Wednesday that its net income was $219 million, or 9 cents per share, in the January-March period. That's up from $205 million, or 9 cents per share, in the same period a year ago when the company was still private.

Revenue grew to $1.46 billion from $1.06 billion, above analysts' expectations of $1.44 billion.

Excluding special items, mainly related to stock compensation expenses, Facebook earned 12 cents per share, matching the average of analyst expectations, according to FactSet.

Menlo Park, Calif.-based Facebook said mobile advertising revenue was 30 per cent of its total ad revenue, amounting to $375 million. That's up from 23 per cent, or $306 million, in the fourth quarter.

Investors had been worried about Facebook's ability to grow mobile revenue since before its initial public offering nearly a year ago. The number of people who access Facebook on smartphones and tablet computers is growing quickly, but Facebook didn't begin showing ads to mobile users until last year.

Facebook's mobile expansion impressed Sterne Agee analyst Arvind Bhatia. "They are making the transition to mobile faster than anyone anticipated," Bhatia said. "It seems like they are delivering."

Bhatia thinks Facebook will fare even better on mobile devices once Zuckerberg firms up its plan to make money from the growing audience checking into Instagram, a photo-sharing service that the company bought last year for $521 million. The analyst believes Instagram will play a bigger role in Facebook's business next year.

Wedbush analyst Michael Pachter said the results are likely to quiet skeptics who doubted Facebook's ability to mine its growing mobile traffic for revenue. He was particularly impressed by the 23 per cent increase in Facebook's mobile ad revenue, even though the company's overall ad revenue for the period dipped 6 per cent from the final three months of last year.

"Their mobile business is probably bigger than any mobile business on the planet other than the (wireless telecommunications) carriers and Google," Pachter said.

Facebook started showing mobile advertisements in early 2012. In the third quarter of last year, the company generated 14 per cent, or $153 million of its advertising revenue from mobile. In the fourth quarter mobile ads represented to 23 per cent, or $306 million.

Research firm eMarketer says Facebook's share of the U.S. online advertising market is growing. This year, the company is expected to take a 6.5 per cent share of U.S. online ad spending, up from 5.9 per cent in 2012. Still, that figure is far behind Google Inc.'s 41.6 per cent.

On the mobile front, eMarketer expects Facebook to take a 13.2 per cent share of U.S. ad revenue, up from 9.5 per cent in 2012, the first year it made any money from mobile ads. Though Facebook is No. 2, it is far behind Google in U.S. mobile advertising. EMarketer expects the online search leader to take a 54.7 per cent share of U.S. mobile advertising revenue this year.

The company also grew its user base during the quarter. This has also been an area of some concern to investors amid chatter of "Facebook fatigue," especially among younger users, surfacing in recent months. But Facebook said its monthly user base grew to 1.11 billion accounts as of the end of March, up 5 per cent from 1.06 million at the end of December.

The number of users who access Facebook every day, on average, grew 8 per cent to 665 million in March, from 618 million in December.

Gartner Inc. analyst Brian Blau said the ongoing growth of daily users suggests that the service is a tough habit to break.

"The network remains in full force," Blau said. "You have to give them a lot of credit."

That doesn't mean there won't be concerns about some Facebook users, especially teenagers, migrating to other mobile applications and digital outlets to hang out with friends and share slices of their lives, said Forrester Research analyst Nate Elliott.

"There is always going to be something new in social," Elliott said. "The question is how much of it is a threat to Facebook? All Facebook can do is keep those users coming back and make money off those users. And Facebook seems to be doing both of those things reasonably well."

Facebook said the monthly user base of Instagram, the photo-sharing app it acquired

Facebook's stock rose 12 cents to $27.55 in after-hours trading. The stock closed down 34 cents on Wednesday, up 3 per cent since the beginning of the year compared with an 11 per cent increase for the Standard & Poor's 500 index. Facebook went public on May 18, 2012, at $38 per share, a price it hasn't hit since.