Nearly one in five Americans depends on their cellphone for consistent Internet access, while a small but growing number of people have their phones as their only means of accessing the Web.

Those who are younger, poorer and those with less education are more likely to rely on their phones for Internet access, according to a report being released Wednesday by the Pew Research Center. Blacks and Latinos are also more likely than whites to lack other means of accessing the Internet.

“The traditional notion of ‘going online’ often evokes images of a desktop or laptop computer with a full complement of features, such as a large screen, mouse, keyboard, wires, and a dedicated high-speed connection,” the report said. “But for many Americans, the reality of the online experience is substantially different.”

On the plus side, at least smartphone penetration is growing, a move that has helped bring the Internet in some form to those without home access. Nearly two-thirds of Americans have smartphones, up from just over a third as of 2011, Pew said in its report.

The growing population of smartphone-dependent Internet users represents both challenges and opportunities. While people count on their phones to access health information, check bank balances or find news and job opportunities, the content is not always well suited to those who don’t have any PC access.

Financial constraints also loom large for those counting on their smartphones. According to Pew’s research, 23 percent of smartphone owners have had to either cancel or suspend service at some point due to cost, while 15 percent say they frequently reach their maximum data limit.

“The connections to online resources that smartphones facilitate are often most tenuous for those users who rely on those connections the most,” said Pew senior researcher Aaron Smith.