Pulmonary mucinous cystic tumor of borderline malignancy is very rare and distinguished from bronchogenic cyst or adenocarcinoma of bronchoalveolar type. We present the case of a 63-year-old woman with a right lower lobe mass, found by chest radiographs. The preoperative diagnosis was made as bronchoalveolar cancer by percutaneous needle aspiration of mass. Right lower lobectomy and lymph node dissections were performed. The lobectomy specimen contained variable sized multilocular cystic mucous masses, filled with mucus. Microscopically, the cystic masses are lined with tall columnar mucinous epithelium but some area contains focal cellular atypism and bronchoalveolar cancer like foci. This foci are lack of cellular atypism consistent with bronchoalveolar cancer cell. After lobectomy the patient has remained free from recurrence and distant metastasis for following 12 months period. Pulmonary mucinous cystic tumor of borderline malignancy appears to have a favorable prognosis and should be distinguished from other lung neoplasms.