Many smartphone owners use the devices as shopping tools, increasing pressure on physical stores to compete instantaneously with online retailers, analysts say.
Two-thirds of owners shop from their mobile devices, a report released Wednesday by comScore Inc., a digital research firm based in Chicago, said.
One of the most common uses for the smartphones is comparing prices, an activity seen as a threat to brick-and-mortar stores' sales and profits.
"Mobile phones are empowering consumers to find the best prices on the things they want and to compare among merchants," Mark Donovan of comScore told the Chicago Tribune. "We've been able to do that on a PC for a long time."
The rise in price comparison apps has caught most retailers off-guard.
While retailer's mobile presence is up from last year -- when 12 percent had a mobile Web site and 7 percent offered apps -- they still need to catch up, Daniel Burrus, chief executive officer of Burrus Research, based in Milwaukee, said.
"For the first time in history, we have our primary computer with us at all times," Burrus said. "Our smartphone is becoming our primary computer. Before that it was our laptop, before that it was our desktop, and before that it was the mainframe. This big shift is happening, and retailers need to wake up to it. It isn't a fad."