A 58-year-old man was admitted to our hospital for detailed examination of continuous cough. On a chest X-ray film, abnormal shadow was detected in the right lower lung field. Preoperative examination findings didn't lead to a definitive diagnosis. Under thoracoscopy partial resection of the lung was performed to rule out a malignant lesion. Intraoperative pathologic finding revealed a granulomatous lesion. And, final pathological diagnosis showed to be a pulmonary dirofilariasis. His postoperative course was not eventful. On 20 th day he discharged postoperatively. Now, under the Pet-boom the disease has been reported increasingly. But it is difficult to find the disease preoperatively. So, it is real to be operated for differentiate from a malignant lesion. Recently in many cases open lung biopsy, has been undergone with less invasive procedure such as thoracoscopy and VATS. It will be mainstream in future.