We experienced a case of benign clear cell tumor, a very rare form of lung tumor. A forty-year-old male complained of non-specific right flank pain for 1 month prior to admission. Under the suspicion of a benign lesion, an exploratory thoracotomy was done. Since the first case was reported in 1963 by Leibow and Castleman, about 40 cases have been reported worldwide by 1993. Basically it was believed to be a benign lesion but in certain cases, it showed malignant behavior. Simple surgical excision is satisfactory to this benign lesion. But close long-term follow up is mandatory. We report this first case in Korea with the review of literature.