Bone scintigraphy in polyostotic fibrous dysplasia typically demonstrates large areas of diffusely, often unilaterally, increased activity involving mainly long bones, ribs, and skull. It serves to demonstrate the multifocality of the disease, especially when only a mono-ostotic lesion is clinically suspected. The authors present the case of a patient who was suspected of suffering from metastatic bone disease after bone scintigraphy demonstrating multiple, discrete, focal increased areas of activity. A bone biopsy from a rib lesion disclosed fibrous dysplasia, and an extensive search for malignancy ruled out metastatic disease. The authors suggest that polyostotic fibrous dysplasia can imitate metastatic bone disease and that this pattern, although uncommon, should be recognized.