Fibrous dysplasia; is a benign, slow progressive fibroosseous mass of the skeleton, mostly involving the craniofacial joints and long bones. We present a case of monostotic, giant fibrous dysplasia excised by forming a tunnel with two different minimal incisions (tunnel method). A fifty four year-old women was admitted to the outpatient clinic with the complaint of chest pain for the last one month. The postero-anterior chest X-ray revealed a mass lesion that started at the posterior of the right second rib, and extending through the entire rib and causing expansion. Computed tomography of the thorax revealed an 18- 20 cm mass lesion that completely invaded the right second rib, causing expansion of the rib and increased sclerosis, extending to the parietal pleura, compressing the lung parenchyma without deteriorating the integrity of the bone cortex. First, with a high level parascapular incision, the giant mass lesion located in the second rib was separated from the vertebra with safe margins. Later, with an axillary minithoracotomy, by seeing the lesion through the chondral section, the mass lesion was completely excised with intercostal structures and parietal pleura. In the postoperative period, flail chest developed in front of the chest wall was treated with conventional methods. After pathological examination of the specimen, fibrous dysplasia was reported as tumor negative in surgical margins. Although asymptomatic thoracic wall fibrous dysplasia is a benign lesion, surgical resection should not be avoided because of its potential to develop into malignancy.