A case of metastatic mucoepidermoid carcinoma of the lung, originating from the hard palate, was diagnosed by sputum and bronchial washing cytology. Although the cytologic features of mucoepidermoid carcinoma have been well described, it is easy to confuse mucoepidermoid carcinoma with the more common primary adenocarcinoma or squamous cell carcinoma of the lung. The features distinguishing mucoepidermoid carcinoma from other primary neoplasms include 1) mucus-secreting cells individually and in clusters admixed with other cell components, 2) epidermoid cells identified by the presence of abundant spread-out cytoplasm and an oval dark nucleus and 3) intermediate cells resembling normal ductal epithelial cells with moderate-to-scanty cytoplasm, a central, round vesicular nucleus and a prominent nucleolus. The morphologic features of metastatic mucoepidermoid carcinoma in this case were similar to those of primary salivary mucoepidermoid carcinoma.