CT scans are used by doctors to get to the core of a problem by creating a 3D image of the most inaccessible nooks of the body.
But the beams of ionising radiation can cause cellular damage.
A fresh analysis of 2013 research is being presented by researchers from the University of Melbourne at the World Congress of Public Health in Melbourne.
They said the radiation risk was much greater than previously acknowledged.
The results indicated that most of the excess cancers occurring more than two years after a CT scan were caused by radiation from the scan.