The aim of this case series was to reveal the difficulties in diagnosing fibro-osseous lesions with radiological and histopathological examinations and quantify the potential risk of infection to fibro-osseous legions. To analyze the concordance between radiological and histopathological diagnoses, this retrospective case series included patients who were clinically diagnosed with fibro-osseous lesions via radiological findings and excluded the patients who did not undergo histopathological examinations. This study also included the patients in whom histopathological results confirmed fibro-osseous legions when preoperative radiological diagnosis did not include fibro-osseous legions. Eleven patients (three men, eight women; median age 24.5 years, range 15-57 years) were enrolled. Although radiological diagnoses of fibrous dysplasia (FD) corresponded with histopathological diagnoses in seven patients, mismatches between radiological findings and histopathological results were found in three patients. In one patient, suspected diagnosis with radiological examinations was malignant lymphoma or FD. In two patients, the histopathological differentiation between FD and ossifying fibroma (OF) was difficult. One patient had lesion recurrence which was suspected to be OF with surgical findings and postoperative course after the initial surgery. In three patients, infections of FD were found. Preoperative diagnosis of OF with radiographic feature of unilocular radiolucency is difficult. In cases in which histopathological differentiation between FD and OF is difficult, operative findings should be used because OF is often found to be well-encapsulated and easily enucleated. Bone in FD showing mixed radiolucent-radiopaque may be vulnerable to infection.