Mucocele is a characteristic swelling of frontal sinus, ethmoid sinus which contains mucous secretion. It may produce orbital complication such as orbital cellulitis, conjunctival edema and eyelid swelling as the cyst is progressively expanded. Authors experienced a case of giant mucocele in frontal sinus, which was found 65 year-old female. The case was treated external frontal approch & intranasal ethmoidectomy with intranasal Nelaton catether insertion. So, we present this case with a brief review of the literature.