We present two cases of osteoid osteoma affecting a lumbar vertebral body and the sacrum, being both in a very infrequent localization and difficult diagnosis. We found the scintigraphy to be of invaluable assistance in revealing the presence of this small nodular lesion of the spine, and the computed axial tomography (CAT) scan study was likewise useful for its precision in localizing the tumor as a basis for deciding upon a viable surgical approach. Without such techniques, correct diagnosis may be made too late. In our experience, surgical resection of the osteoid osteoma brings about immediate relief of the symptoms.