The Apple iPhone now represents almost one third of all touchscreen phones in the US, according to a new study.

Of all touch phones in the country, 32.9 percent are iPhones, according to ComScore report released on Monday.

Apple's success comes as the touchscreen market itself has grown dramatically in the past year. The number of phones in American hands has jumped 159 percent from 9.22 million in August 2008 to 23.84 million just one year later.

By comparison, the entire US smartphone market grew by 63 percent to 33.78 million, or enough for touchscreen phones to represent a large section of the smartphone business where they were just a minority before.

Touchscreen phones have quickly gained adoption as new devices have flooded the mobile marketplace, said Mark Donovan, comScore senior vice president of mobile.

The iPhone's market share was nearly four times larger than the next largest device family, the LG Dare. LG Voyager ranked third, with 7.8 percent of the market, followed by the Blackberry Storm, 7 percent, and Palm's Treo with 6.5 percent.

Adoption of touchscreen phones is expected to accelerate even further as more touchscreen phones, particularly devices that use Google's Android operating system like the Motorola Droid, reach the market.

According to the report, among the users of smartphones, more than half are under 35 years old. Of these, 51.4 percent of smartphone owners are under the age marker, while 57.7 percent of touchscreen phone owners fit into that age group.