Osteoma is a benign, usually asymptomatic bone tumour, frequently arising in the nose and paranasal sinuses. Surgical treatment is required when the patient becomes symptomatic or presents ophthalmological or neurological complications. Although an endoscopic approach is increasingly used, depending on the size and site of the osteoma, open surgery may be preferable and remains the standard treatment. This technical note describes a case of giant osteoma of the frontal sinus that required a bicoronal approach with reconstruction by a custom-made titanium prosthesis.