The study is taking place in five European countries and will look at cell phone use at 10, 20 or 30 years.
Scientists say that with many cancers taking longer to develop there was a need for a longer term study.
Several studies have already concluded that scientific evidence to date does not support the idea that any adverse health effects are associated with the use of cell phones.
However, researchers say that most people have not had mobile phones for more than 10 years, so the question has to be addressed.
