WDFA(Well-differentiated fetal adenocarcinoma) histologically resembles pulmonary blastoma. It is also thought to be a subtype of pulmonary blastoma, which has differentiated epithelial features resembling the fetal lung among its epithelial features and sarcomatous features. We recently encounted a patient who underwent surgery for WDFA. A 19-year-old man had a mass shadow in the upper lobe of the left lung. The tumor was diagnosed as pulmonary blastoma as a result of fine needle aspiration biopsy, and left upper lobe lobectomy was performed. No sarcomatous features was observed on postoperative histologic assessment, and the patient was diagnosed as having WDFA. This case is reported with a discussion of the literatures.