Osteoblastoma (OB) and osteoid osteoma (OO) are benign bone-forming tumors frequently involving vertebrae and long bones of the extremities. Because of their similar histopathological features, distinction between OB and OO is mostly based on size criteria. CT and MRI represent the cornerstone of noninvasive diagnostic procedures, as they provide excellent morphologic details and often obviate the need for confirmatory biopsy. Bone scan is a complementary, highly sensitive functional technique particularly useful for detection of vertebral OO. F-18 FDG PET/CT could have potentiality in diagnosis and post therapeutic evaluation of patients with OB and OO. We report MRI and dynamic F-18 FDG PET/CT results obtained before radiofrequency or laser ablation from 3 patients with an OB of the right L5 pedicle, an OB of the left talus and an OO of the right acetabulum. Both patients with OB underwent posttherapeutic evaluation to confirm the effectiveness of percutaneous radiofrequency ablation.