The French scientists found that people who use their mobile phone for more than 15 hours per month over five years on average have between two and three times more risks of developing brain cancer - glioma and meningioma tumours - than those who rarely use their mobile phone.
The study, published in the Occupational and Environmental Medicine section of the British Medical Journal, looked at 253 cases of glioma and 194 cases of meningioma reported in four parts of France between 2004 and 2006.
These patients were matched to 892 healthy individuals.
The comparison found a higher risk among the intensive mobile users, especially those who use their phones for their work.
Another new finding was that cancer can occur on the opposite side of the brain to the side where the phone is used.
"It is difficult to define a level risk," said the paper's coauthor Isabelle Baldi of the University of Bordeaux, "especially as mobile phone technology is constantly evolving."
The use of mobile phones has considerably increased since 2000, meaning more radiowaves surrounding us, although the intensity of waves emitted by phones has decreased.