Updated with stock price.

NEW YORK ( TheStreet) -- Google ( GOOG) took another slice of the Internet advertising pie Monday with a $750 million all-stock acquisition of closely held mobile-ad specialist AdMob.

The move comes as Google's Android smartphone operating system, including Motorola's ( MOT) Droid phone, starts to catch on in the U.S. and Europe as a rising force in wireless software.

Google's aim is to extend its dominant desktop-search service to mobile phones, where rivals Microsoft ( MOT) and Yahoo! ( YHOO) have yet to develop a strong plan.

The No. 1 Internet search ad shop says the AdMob deal will help Google "develop more effective tools for creating, serving and analyzing emerging mobile ads formats," according to a press release Monday.

"We believe that great mobile advertising products can encourage even more growth in the mobile ecosystem. That's what has us excited about this deal," Google Product Chief Susan Wojcicki wrote on the Google Blog.

Google acquired display ad giant DoubleClick for $3.1 billion last year, and in-game video advertising shop Adscape for $23 million.

Google shares, after hitting a 52-week high of $562.50 earlier Monday, were trading at $561.29, up $10.19, or 1.85%, shortly before 3:30 p.m. EST.