Retailers with suspicions that smartphone-wielding consumers inside their stores are pricing products at competitors and buying elsewhere may be onto something. According to a survey of 360 smartphone and tablet users, 40.6% of them have done just that, says Prosper Mobile Insights, a mobile commerce technology company that commissioned the survey.

“The data reveals that many mobile users are taking advantage of their smartphones and tablets while shopping, and some of them are walking out the door to make a purchase at another retailer,” Prosper Mobile Insights says.

More troubling for store retailers is that fewer consumers—30.6%—compared prices inside a store and bought a product from that retailer.

Consumers used their smartphones inside stores for other activities, too. Many—35.8%—read product reviews. Also popular with 29.7% was scanning a Quick Response, or QR, code, which is a type of two-dimensional bar code that links physical products or signs to mobile web content, to get more information about a product.

And 26.7% of consumers use their smartphones to check in using location-based apps, such as Foursquare, to get a discount at the retailer, the survey found.

“Mobile technology is posing an in-store shopping challenge for retailers as it provides competitor pricing at consumers’ fingertips,” said Phil Rist, Prosper executive vice president of strategy. “Consumers are now able to ask questions of the sales staff, touch the product, check for the best price on their mobile device and then walk out the door. The best way for retailers to counter the comparison shopper is to offer an in-store price match or other promotion to influence them to purchase.”

Survey Sampling International conducted the survey Dec. 29 through Jan. 3.