Subcranial approach is a useful procedure in the management of limited anterior skull base tumors. But the posterior and superior visualization may be limited, in ethmoid malignancies with a large intracranial extension. A 55-year-old male patient, a case of an ethmoid malignancy, with a large intracranial component was resected with adequate margins by a subcranial approach. The coincident pneumosinus dilatans helped the surgical resection. This case demonstrates that assessment of pneumatization of the frontal sinus is as important as the size and extent of the tumor, while deciding an anterior skull base surgical approach. Even large malignant lesions may be approached subcranially if the frontal sinus is proportionately large. Pneumosinus dilatans, though rare, can be used to the benefit of the patient in selecting a less invasive approach.