Chronic frontal sinus disease, which do not respond to medical treatment, has been treated by surgical methods. Riedel’s radical sinusectomy shows excellent success rates, but results in flattening of the forehead. Lynch-Howarth frontal sinusectomy damages the bony framework of nasofrontal duct, and results in relatively high recurrence rate. Frontal osteoplastic flap operation, which has been widely used, provides excellent frontal sinus exposur and shows little recurrence rate. But fat obliterated sinus is always radiographically opaque, which makes the diagnosis of recurrent disease difficult by either palin films or CT. Recently, endoscopic frontal sinus surgery has been reported with good results. But long term follow up study is still required. We used the combined method of frontal osteoplastic flap operation and endoscopic frontal sinusotomy, in one case of frontal mucocele which has the history of nasal polypectomy and intranasal ethmoidectomy, and in another case of chronic frontal sinusitis which was recurred after endoscopic frontal sinus surgery. And we had good results in these two cases.