While the Galaxy S III is helping Samsung (005930) grow its presence on the mobile web, the company is still well behind Apple (AAPL) when it comes to usage. Mobile ad firm Chitika has released new numbers showing that the Galaxy S III’s share of overall Samsung ad impressions in North America has risen significantly since its initial release, jumping from less than 3% on June 18th to over 11% on August 6th.

Chitika says that the Galaxy S III “has quickly surpassed the Galaxy Nexus in activity, and is hot on the tails of other Galaxy S models” and “is likely that adoption of the device will continue to increase in the future as the holiday season approaches and Android aficionados upgrade their phones.”

But even with the surge in Galaxy S III mobile Web use, Samsung as a whole still only generates roughly one-fourth as many mobile ad impressions in North America as Apple does with its assorted iPhone models. Despite this disparity, Chitika says that Samsung remains “the iPhone’s closest challenger for the coveted top spot” in mobile ad impressions, and says the companies’ rivalry will be “one of the most intriguing contests in the smartphone market this year.”

via Samsung mobile web presence increases, still trails iPhone.