Once again Apple’s iOS is the most lucrative platform on Opera’s mobile ad platform, with an average eCPM (effective cost per thousand impressions) of $1.64, according to the web browser maker’s Q3 2012 State of Mobile Advertising report.

The Oslo, Norway-headquartered company’s mobile ad platform, which touts itself as world’s leading mobile ad platform, serves more than 10,000 mobile sties and apps and delivers more than 40 billion ad impressions per month.

Platforms below iOS’s eCPM of $1.64, which was 25 percent more than the worldwide average of $1.31 eCPM, was RIM at $1.06, Android at $0.88 and Nokia’s Symbian OS at $0.37.

In terms of traffic and revenue, iOS devices accounted for 46.37 percent of total ad traffic and 58.40 percent of revenue. Android made up 25.66 percent of traffic for Opera and 16.79 percent of revenue, which are traffic and revenue percentages that are far fewer than that of Apple’s suite of iOS devices. Microsoft’s Windows Phone devices, which were shoehorned into “Other,” represented 20.04 percent of traffic and 19.67 percent of revenue, with an eCPM of $1.28.

At the Masters of Monetization session at this week’s Appnation event in San Francisco, Mahi De Silva, executive vice president, consumer mobile for Opera, said despite there being more Android devices than iOS in the ecosystem, people use more apps on iOS than Android. He added that advertisers want an audience they can reach and it’s easier to integrate ads on iOS versus Android, so advertisers tend to favor iOS.

The iPad remained the most lucrative Apple device ($3.96 eCPM in Q2 2012), averaging $4.42 eCPM, which is more than double the eCPM of the iPhone at $1.48 and more than triple the eCPM of the iPod Touch at $0.82.

“If you look at some of the big media companies, on iPad they are getting CPMs they never saw on the desktop because of the rich-media experience on the device,” said De Silva at Appnation.

Between mobile apps and web, apps grabbed the two-thirds majority of advertising dollars, generating 73 percent of revenue for Opera. The remainder of ad revenue came from mobile web.

Publisher category-wise, the business, finance and investing category generated the most revenue per impression compared to other publisher categories while the sports category displayed the most growth.

Opera took a closer look at the U.K., one of its best performing regions, in this report. Surprisingly, BlackBerry traffic in the U.K. is almost four times higher than BlackBerry traffic in the U.S., with 14 percent of total traffic in the U.K. coming from RIM devices compared to 4.40 percent in the U.S. Also, publisher categories the U.K. favored include the arts and entertainment and the health, fitness and self help categories.

Publishers using Opera’s mobile ad platform include Pandora, Shazam, and CBS, and some advertisers include Samsung, Walmart and American Express.

Data for this report was collected from Opera’s subsidiaries including AdMarvel, Mobile Theory, and 4th Screen Advertising, three mobile advertising companies it purchased for upward of $100 million in total.

Opera says it remains on track to generate more than $400 million for mobile publishers in 2012, which is a large increase over 2011 when it generated $240 million.