A 27-year-old man presented with symptoms of chronic postnasal drip and nasal obstruction, which had begun one year earlier. He had undergone an ophthalmologic operation due to inferior orbital wall fracture 12 years ago. During physical examination, mucopurulent discharge was observed from the right middle meatus. On the paranasal sinus computed tomography, a sheet-like foreign material was observed inside the right maxillary sinus and haziness was found in the right maxillary, ethmoid, and frontal sinuses. Endoscopic sinus surgery was performed and a silastic sheet, which had been inserted during previous surgery, was removed. After surgery, the patient’s symptoms disappeared gradually. We report a case of maxillary sinusitis that occurred after orbital wall reconstruction with a silastic sheet and discuss about the efficacy of the silastic implant.