Paget disease (PD) of bone is a benign but chronic disorder of bone metabolism. We report a case of an 85-year-old man with several fractures in the pelvis and radiograph raising suspicion of metastases. An 18F-NaF PET/CT demonstrated high 18F-NaF uptake in the same regions. The integrated assessment of imaging findings, supported by biochemistry, allowed diagnosing PD. The 18F-NaF PET/CT is a supplementary diagnostic instrument in the diagnosis of PD, and use of 18F-NaF PET/CT in this context, especially finalized to the differential diagnosis with metastatic lesions, requires the physician to be familiar with imaging patterns of this disease.