The study found that on average French workers spent 57 minutes per day on the Internet for personal use, or 59 percent of the total time they use the Web.
Conducted by Olfeo, a firm which sells software that allows companies to filter and secure Internet traffic, said the personal use of the Web by employees caused a 13.6 percent productivity loss to firms.
Olfeo found that upon their arrival to work French employees like to consult news sites and catch up on social networks.
During lunch hours they favour watching television episodes online, listening to the radio or playing online games.
Before heading home French workers check traffic and weather reports, or kill time on entertainment sites.
The study, conducted in 2012 based on 100 firms with 80,000 employees, found that French workers who stay at the office after 7 pm used the Internet to work.
The social networking site Facebook was the top website for personal traffic at French workplaces, followed by the video-sharing site YouTube.