Despite challenging economic conditions, smartphones continued to gain significant market share worldwide over the past six months, rising from 26 percent to 33 percent of requests in February, according to AdMob's February 2009 Mobile Metrics Report .

The launch of HTC's T-Mobile G1 and the BlackBerry Storm propelled increases in Google's Android and Research in Motion's operating system requests in the United States. This growth is based on mobile Web usage, not the number of handsets sold, and demonstrates the high consumer engagement with these touch-screen devices.

"This growth in smartphone usage demonstrates the opportunity for marketers to create compelling mobile ad campaigns that take advantage of capabilities these powerful devices to engage with consumers," said Nicole Leverich, spokeswoman for AdMob, San Mateo, CA.

The top handsets on AT&T and Sprint are also touch-screen devices: the Apple iPhone and the Samsung Instinct.

Worldwide, the top five smartphones are the iPhone, Nokia N70, BlackBerry 8300, Nokia N80 and Nokia N73. The top five U.S. smartphones are the iPhone, BlackBerry Curve, BlackBerry Pearl, Palm Centro and HTC's T-Mobile G1 with Google.

The BlackBerry Curve has overtaken the Pearl as the No. 1 Research In Motion device. The BlackBerry Storm is the No. 1 device on Verizon Wireless, with 14 percent of requests.

Nokia's Symbian lost market share, but is still No. 1 worldwide with 43 percent of requests.

The Samsung BlackJack II is the top Microsoft Windows Mobile device worldwide. Six of the top 10 Windows Mobile devices are from HTC.

Android accounts for 5 percent of the U.S. smartphone market. The iPhone generated 33 percent of smartphone traffic worldwide and 50 percent in the U.S.

A whopping 97 percent of BlackBerry requests came from their OS Version 4.2 or higher. These devices will all have access to BlackBerry App World when it goes live.

Symbian and Windows Mobile have a significant percentage of their user base on devices running old versions of their OS. These devices many not have access to their application stores when they launch later this year.

AdMob stores and analyzes handset and carrier data from every ad request in its network to optimize ad serving. Each month, the Mobile Metrics Report aggregates this data to provide insights into major trends in the mobile ecosystem.

"The upcoming launch of application stores for RIM, Nokia and Windows Mobile devices will also create new opportunities for advertisers to reach their desired audience in fun new ways," Ms. Leverich said.