Among a range of questions relating to technology, it asked more than 1,000 US online consumers to provide a true/false answer to a statement concerning privacy.
That meant "there is a deeply embedded and long-standing confusion among consumers when it comes to privacy policies and the protections they afford," Pew warned.
Joseph Turow, a professor at the Annenberg School for Communication, University of Pennsylvania, added that it's not surprising consumers get confused because privacy policies are often so laden with jargon that they become "unreadable".
"They are filled with jargon that is meant to be understandable only to the people writing them, or to people who work in the advertising industry today," he said.
He also explained that consumers often don't realise just how much personal information can be gleaned from data mining tools.
"The general sense among marketers is that people understand that their data is being used, but we've found in our research that people don't truly understand how data mining works.
"They may realise that one or two pieces of their information are being given out; what they don't realise is that those one or two data points can be linked with other sources to uncover information they would have never given out in the first place."
Another recent survey by the Pew Research Center found that a full 91% of US citizens feel they have lost control over how their personal information is collected and used by companies.
Meanwhile, a separate poll conducted in 24 countries for Canada's Centre for International Governance Innovation (CIGI) found 64% of the more than 23,000 respondents are more concerned about their online privacy than a year ago.
However, the survey also found that 37% of users share personal information with private companies online all the time and say "it's no big deal".
Data sourced from Pew Research Center, CIGI; additional content by Warc staff