The majority are satisfied with free or preloaded games, according to the report, which was released Tuesday. The findings were based on a survey of more than 6,700 teenage and adult wireless subscribers.
The report also notes that, among survey respondents, the average gaming session is 11 minutes long.
About half the cell phones in use in the United States are capable of downloading games, the report said. And 27 percent of people with those phones use them to play games, up from 20 percent last year. Teens are three times as likely as adults to play games, according to NPD.
The report adds that there's plenty of room for growth, noting that 6 percent of non-gamers surveyed said they're interested in using their phones to play games during the next year. The reason most often cited for the increasing interest, the study said, is the desire to "kill time or alleviate boredom."
NPD also said that people who buy mobile games prefer paying for single-game downloads and don't seem to be clamoring for monthly subscription plans.
Still, though they don't seem eager to pay for games, mobile gamers do tend to spend more money on handsets--an average of 57 percent more, according to the study.
Moreover, gamers use 48 percent more wireless minutes than non-gamers, ending up with monthly wireless bills that are 22 percent higher than that of the average subscriber, NPD said.