We encountered two cases in which pulmonary eosinophilic granuloma improved after cessation of smoking. The patient in case 1 was a 39-year-old woman. She smoked 10-15 cigarettes a day for 20 years. The patient in case 2 was a 19-year-old man. He smoked a pack of cigarettes a day for 5 years. CT revealed cystic lesions and small nodular lesions predominantly in the upper and middle lung fields. Diagnosis was made by thoracoscopic lung biopsy in case 1 and by transbronchial lung biopsy in case 2. After smoking cessation, symptoms, CT findings, and vital capacity of both patients improved remarkably. Smoking cessation may have been related to the improvement in these patients.