58% of U.S. adults who own a smartphone and/or tablet say they use their device to help them with in-store shopping, either by looking up information in advance or while inside the store, according to a recent survey by digital marketing, analytics and optimization firm Maxymiser. However, if mobile web sites those shoppers visit don’t meet their expectations—most importantly, that the site is easy to use and the pages load fast—9% of them say they will never return to the site and 30% say they’ll visit a competing mobile web site instead, the firm says.

Maxymiser surveyed online 1,000 U.S. adults who own a smartphone, tablet or both between July 2 and July 5 for its “Mobilizing the Retail Shopping Experience” study. Here is what respondents said when asked the top criterion for determining whether to stay on or return to a retailer’s mobile web site, with the percentage of consumers who call it their No. 1 priority:

• The site is easy to use, 45%
• Pages and images load fast, 20%
• Search and navigation are easy to find and use, 12%
• Images and text fit on the smaller screen, 6%
• Few clicks are required to obtain more information, 5%
• The site scrolls only in one direction, 4%
• Buttons are large and easy to see, 3%
• The cart updates instantly, 3%
• The checkout button is easy to find, 2%

“One of the more surprising statistics is that a mobile experience requiring fewer clicks to get more information is only important to 5% of mobile shoppers,” says Paul Dunay, global vice president of marketing at Maxymiser. “What’s most interesting about this stat is not the number itself; It’s another indicator of how important data is in providing clarity on what mobile consumers really care about, as opposed to what brands might assume their mobile audience wants.”

Mobile shoppers in the survey tend to visit three types of retail web sites on their devices in advance of in-store shopping more than others: 46% of respondents say they visit an electronics retailer’s mobile site before going to a store, 26% say they visit a clothing site and 15% say they visit a food site. And the top three mobile shopping activities among respondents are: make a purchase (31%), comparison shop (19%) and find a store location (14%).