The mobile advertising network, InMobi reports that tablet impressions have been growing nearly twice as fast as smartphones in North America.

The report finds that Apple clearly dominates, with iOS tablet devices currently commanding 71% of the overall impression share, followed by Android with 29%. However, Apple lost 10.8% of its market share to Android, highlighting the competitiveness of the market.

Despite entering much later to the market than many of its competitors, the Amazon Kindle Fire performed second (9.2%) to the Apple iPad (70.8%) in Q1 2012. The Asus Eee Pad sits in third (5.2%) with a positive point change of 2.5% from Q4 2011 to Q12012.

Anne Frisbie, Vice President and Managing Director, North America, InMobi, comments: "Richer web browsing experiences are achieved from the larger screen sizes and the reduced cost of tablet ownership is increasing their popularity.  We are seeing smart brands raising the bar for advertising on tablets, and were very excited to see an InMobi ad campaign featured in the recent IAB Tablet Creative Showcase."

North America Tablet OS ad impressions

North America Top Performing tablets, total ad impressions