Fibrous dysplasia accounts for approximately 7% of benign bone tumours and is a developmental disorder of unknown aetiology. Malignant transformation has been reported in 0.4% of all cases of fibrous dysplasia, and the use of 18F-fludeoxyglucose positron emission tomography/CT scan in the evaluation of malignant transformation has not yet been established. A 72-year-old male with a long-standing history of polyostotic fibrous dysplasia presented with chest and back pain and was evaluated with a 99mTc-methylene diphosphonate bone scan as well as an 18F-fludeoxyglucose positron emission tomography/CT scan to define the extent of bone involvement and assess for possible malignant transformation. We present the imaging findings as well as the long-term follow-up of this case.