The accurate diagnosis of fetal thoracic tumors still remains unclear despite the progress in imaging technology, The differential diag­nosis between tumors and congenital anomalies of the fetus respiratory system, largely depends on the diagnostic approaches involved, We report a case of a 25-year-old woman, gravida 3 para 0, who was seen at the 23^rd gestational week for routine obstetric examina­tion, The ultrasound scan detected a lung mass, occupying the whole left hemithorax with a significant shifting of the mediastinum exhibiting features compatible with cystic adenomatoid malformation (CAM). No other congenital anomalies were noted. Color Doppler ultrasound failed to detect any blood supply to the mass. Amniocentesis disclosed a normal male karyotype. Pregnancy ter­mination was performed according to the parents’ request, with the use of misoprostol and a 500 g dead fetus was delivered. The autopsy fo11owed by detailed histological examination, disclosed the diagnosis of pulmonary sequestration. It is important to emphasize that the initial impression concerning the sonographic appearance and the size of the mass is not always in accordance with the diagnosis of the lesion and the outcome of the pregnancy. These data suggest that in cases of fetal pulmonary tumors, a thorough and comprehen­sive combination of imaging approaches should be employed followed by a pathologic examination of the congenital anomaly in order to establish a definitive diagnosis.