Osteomas are the most common benign tumors of the paranasal sinuses. They are usually localized in the frontal sinus. Giant osteomas of the frontal sinuses are very rare but readily extend into the intraorbital or intracranial cavity, causing serious complications. This is a report of a 14 year-old boy with a bulging in frontal area and asymptomatic giant osteoma of the frontal sinuses. He had a history of minor trauma that had a bulging after 3 months. However, he referred to a plastic surgeon after 15 months. Computed tomography of the sinuses revealed a 3.5 × 6 cm extremely dense bony mass in the frontal sinus that extended into the left orbit and ethmoid sinus. A bicoronal frontal flap was raised with a V-shaped skin incision starting from the tragus placed 5 cm posterior to the hairline. The osteoma was resected completely in the frontal sinus and the anterior wall of frontal sinus was reconstructed with Porex. The patient has not had any complications until the time of writing this report. Titanium mesh may still be a valuable option, but Medpore Porex has shown to be quite effective in this case.