INTRODUCTION: Maxillary sinus mucocele is an unusual clinic entity (incidence of 3-10%), represented by mucous secretion lined by respiratory stratified pavemented epithelium and its origin is mainly secondary to infections, inflammations, surgery, trauma or neoplasia. CASE REPORT: We present a case of maxillary sinus mucocele. Subject of the study is a 74 aged patient referring positive anamnesis for nasal cavity surgery. His symptoms appeared six months ago and he complainted vertical ocular diplopia and ocular tension sensation, without rhinologic complaints. Oculistic examination confirmed an isolated left inferior rectus palsy, and CT showed mucous secretion occupying left maxillary sinus, with bone erosion to the orbital floor until orbital muscles. MRI is the gold standard for differential diagnosis with neoplastic lesions but the patient refused to perform this radio-diagnostic exam. He underwent to Endoscopic sinus surgery, consisting in middle meatal antrostomy and removal of the mucocele. Four months later the endoscopic follow-up showed regular maxillary cavity and regular ocular motility. CONCLUSION: In our opinion the rebuilding of the eroded bone is not mandatory if the integrity of the maxillary upper wall mucosa is respected, and antrostomy with drainage allows to recover ocular and paranasal sinus function.