Mobile commerce sites and apps are changing the way consumers shop, and the number of consumers shopping via mobile is considerable, a new study shows.

In September two-thirds of all smartphone owners shopped in some way on their phones, including comparing products and prices, searching for coupons, taking product pictures, and locating a retail store, finds web and mobile measurement firm comScore in its comScore Mobile Retail Advisor report. 38% of smartphone owners have used their phone to make a purchase at least once—that’s 34.2 million U.S. consumers, comScore says.

“Fueled by smartphone adoption, mobile is becoming a central part in the shopping funnel for many consumers,” says Mark Donovan, comScore senior vice president for mobile. “Considering there are currently 90 million smartphone owners in the U.S., retailers without a well developed mobile strategy are not only missing a tremendous opportunity with these customers but also risk becoming obsolete in the minds of these digital omnivores.”

47% of smartphone owners who made a purchase in September bought digital content such as music, e-books, TV episodes and movies, comScore finds. 37% purchased clothing or accessories while 35% bought event tickets. Slightly more than one in three mobile purchasers bought daily deals and gift certificates. 32% purchased electronics, 26% books (physical copies), 24% airplane tickets and 21% flowers.

Mobile shoppers were making purchases everywhere. 56% of smartphone owners who made a purchase in September did so at home, 42% outside of the home (such as at a restaurant or a park) or at work, and 37% while traveling or commuting. Slightly more than one in three made a purchase while in a store, highlighting the increasingly important role mobile commerce is playing in the bricks-and-mortar world, especially as a tool for real-time price and product comparisons, comScore says.