The share of paid search budgets allocated on campaigns optimized for Apple's (NASDAQ:AAPL) iPad and rival tablets increased 40 percent in the second quarter of 2012 over the previous quarter, according to new data published by digital ad management platform Marin Software.

Advertisers and agencies dedicated 7 percent of their paid search spending on tablets in June 2012, compared to 5 percent three months earlier, Marin Software reports.The firm adds that cost per click for paid search ads run on tablets is 18 percent lower than CPC rates for ads running on computers--at the same time, the click-through rate for paid search ads on tablets is 42 percent higher than desktop ads.

Mobile devices now account for 18 percent of all paid search clicks in the U.S., up from 14 percent in the first quarter of 2012: Smartphones yielded 10 percent of all paid search clicks during the second quarter, followed by tablets at 8 percent. Clicks on tablets grew 33 percent quarter-over-quarter.  

"Right now, advertisers are getting the best of both worlds on tablets. The combination of high user engagement and favorable ad performance characteristics is a win-win for marketers," said Marin Software Vice President of Marketing and Partnerships Matt Lawson. "To capitalize on the window of opportunity savvy advertisers will become more device conscious, implementing campaigns directly targeted at tablet users."

Marin Software powers marketing campaigns in 160 countries. More than 1,500 brands manage annualized ad investments in excess of $3.5 billion on the firm's platform.