Adenocarcinomas with micropapillary patterns are generally aggressive and show lymphotropism. Only a few reports on pulmonary adenocarcinoma with micropapillary patterns have described cytologic findings. A 70-year-old Korean woman was admitted to the hospital because of intermittent dry cough and chest pain. Cytology after bronchial washing showed neoplastic cells in small, angulated, cohesive clusters consisting of 3-20 cells without a fibrovascular core. The resected right middle lobe showed a tumor occupying almost the entire lobe. Histologically, about 90% of neoplastic cells proliferated with micro papillary morphology in the background of bronchioloalveolar carcinoma. Cytologic smears of a bronchial washing showing tumor cells in small, cohesive clusters without a fibrovascular core may indicate an adenocarcinoma with micropapillary pattern.