Smartphones make up the overwhelming majority of mobile ad impressions, showing the opportunities available to marketers to target a smaller screen, according to a new study from Millennial Media.

Millennial Media?s latest ?Mobile Mix report? took a look at how impressions break down across both tablets and smartphones. The report also looked at which industries make up the largest percentage of campaigns.

?Seventy-four percent of all impressions on our platform came from smartphones, which is a growth of eight percentage points year-over-year,? said Marcus Startzel, general manager of North America at Millennial Media, Baltimore.

?This is an exciting trend for advertisers, and we are seeing brands increasingly look to run video and rich media ads as a way to engage consumers on these devices.?

In-app opportunity
Millennial Media?s report found that games remain the No. 1 application category by impressions year-over-year.

The other top app categories include music and entertainment, science and technology and social media. In particular, social media increased as a top app category from the No. 4 spot to No. 3 quarter-over-quarter.

Rounding out the top ten categories for apps were communications, weather, news, sports, books and reference and automotive.

Impressions from books and reference and science and technology apps were 15 times higher in the second quarter than they were in the first quarter.

Target on mobile
Apple leads the pack as the No. 1 manufacturer with 31 percent of impression share on Millennial Media?s network.

Samsung devices made up 22 percent of impressions. Eight Samsung devices were included in the top twenty devices for the company.

Rounding out the top three manufacturers was Research in Motion with approximately 13 percent market share. HTC ranked as No. 4 with almost nine percent.

Android made up 46 percent of total impressions, showing how although the operating system has a large footprint, fragmentation is still a problem for the company. IOS devices made up 34 percent of all ad impressions.

When it comes to tablets, 95 percent of impressions came from Wi-Fi networks, showing how the bulk of users are likely interacting with the devices while at home.

The No. 1 tablet on Millennial?s network was Apple?s iPad, followed by Samsung?s Galaxy Tab, Amazon?s Kindle Fire, Acer?s Iconia and Motorola?s Zoom.

?The iPad, Samsung Galaxy Tab and the Kindle Fire were all in the top twenty overall mobile devices on our platform in Q2, and this speaks to the impact tablets have made on the mobile ecosystem,? Mr. Starzel said.

?The growth of tablets has been one of the major trends we?ve seen over the last few years, and we expect this to continue in the future,? he said.

Final Take
Lauren Johnson is associate reporter on Mobile Marketer, New York