Fine needle aspiration (FNA) cytological examination is an appropriate method for the evaluation of pulmonary nodules. In major types of lung cancer, Its diagnostic accuracy is quite high. However, it is sometimes difficult, using this technique, to differentiate between some unusual phenotypes including adenosquamous carcinoma, bronchioloalveolar carcinoma (BAC), neuroendocrine tumor, mucoepidermoid carcinoma, and sclerosing hemangioma. Here, we present a case involving extremely well differentiated adenosquamous carcinoma, mimicking benign lesions, such as pulmonary scar and adenomatoid malformation with squamous metaplasia. The patient was a 68-year-old man presenting with a solitary pulmonary nodule$(1.6 imes1.6cm)$, which was incidentally found at the periphery of the right lower lobe. FNA revealed some clusters of glandular cells with minimal atypia, in addition to squamous cells at a nearly full maturational state. Histological examination verified the cytological diagnosis on a lobectomy specimen. The tumor exhibited a well differentiated adenocarcinoma component, mimicking the bronchioles in scarred lung tissue. and a well differentiated squamous cell carcinoma component, mimucking the squamous cell nests of adenoacanthoma, in the other organs. In the present case, the possibility of adenosquamous carcinoma should have been considered if squamous cells were seen in the FNA from the peripheral pulmonary nodule, even though they appeared to be benign.