Extramedullary hematopoiesis is the production of blood outside of the bone marrow. While it may normally arise in the liver and spleen during the fetal period, it is considered as a compensatory mechanism in adults. Extramedullary hematopoiesis is seen in patients with chronic anemia such as thalassemia, hereditary spherocytosis, most commonly in the liver and spleen, as in the fetal period. On the other hand, intrathoracic hematopoiesis is quite rare. The aim of this study is to discuss this rare condition. A 42-year-old male patient was examined for a mass incidentally detected in the lung during his routine follow-ups. In our patient with no history of diseases except for external thalassemia intermedia, the scattered homogeneous density increments on the posteroanterior chest x-ray were evaluated and his thoracic tomography revealed soft-tissue increments of 7.5 cm in the vicinity of the rib and vertebrae. Extramedullary hematopoiesis should be kept in mind in the differential diagnosis of patients with bilateral masses by the contiguity of the rib and vertebrae. Hematological studies should be conducted in this regard.