Apple and Google's mobile platforms are gaining market-share on rivals, while Microsoft and Palm are continuing to slip.

BlackBerry maker Research In Motion, is still the most popular smart-phone platform in the U.S., with 41.6 percent market-share, according to research firm, ComScore.

Apple's share of the smart-phone market rose to 25.3 percent from 24.1 percent over the same period, and Google, though still in fifth place, saw its share more than double to 5.2 percent from 2.5 percent.

On the other hand, Microsoft slipped to 18 percent share, while Palm saw the biggest losses, with its share dropping to 6.1 percent from 8.3 percent, despite recent price cuts that made its devices among the cheapest on the market.

Vendors shipped 54.5 million smart phones world-wide in the fourth quarter, up 39% from the year-earlier period, according to market-research firm IDC.