Osteomas are benign slow growing tumours of the paranasal sinuses. The frontal and ethmoidal sinus- es are most commonly affected. We present an unusual case of a 42-year-old Malay lady who had a frontal lobe mucocoele, secondary to an extensive frontal sinus osteoma with orbital and intracranial extension, and presenting primarily with orbital proptosis. She was successfully managed by a multi specialty team.