We present a case of benign pediculate mucinous cystadenoma in a 60-year-old man. The tumor, which was connected with the lung parenchyma, was difficult to distinguish from a pleural tumor radiographically. Initially, computed tomographic-guided needle aspiration biopsy was performed to confirm the diagnosis, but this was unsuccessful. Therefore, surgical resection was performed to diagnose and treat the tumor, and pathologic examination of the specimen revealed mucinous cystadenoma. The problems associated with the diagnosis and treatment of pediculate mucinous cystadenoma are discussed in light of this case.