Normal cell phone use doesn't appear to increase the risk of brain tumours – however, intense long-term users could have a higher risk of developing tumours. 

A new study from the Radiation and Nuclear Safety Authority in Helsinki demonstrates that cellular phone use doesn't appear to increase the risk of the most common type of brain tumour, glioma.
The debate over the health risks of cellular phones has raged for years, with different studies coming up with varying results. However, the public remains concerned over the effects, especially considering the risk of brain tumours developing.
Because cellular phones emit radiation, and are used in close personal contact to the body, fears have abounded. One detractor described users becoming aerials for radiation signals simply by putting their phones to their ears.
However, the latest study finds no evidence of increased glioma risk related to regular cellular phone use. Statistics don't change significantly accoarding to duration of use, years since first use, cumulative number of calls or cumulative hours of use.
The study did find a trend, though, towards an increased glioma risk in people who used a cellular phone for more than 10 years, exclusively on one side of the head. Described as "borderline statistical significance", there was a slightly raised risk of a tumour developing on that side of the head.