We report on a 9-year-old boy with neurofibromatosis type 2 and a progressive proptosis of the left eye. Imaging studies revealed a pneumosinus dilatans of the left ethmoidal and frontal sinuses and an adjacent left orbital mass. Incision biopsy of the orbital mass showed a meningiothelial meningioma. Orbital and intracranial meningiomas are frequently associated with pneumosinus dilatans. This report illustrates the relationship of pneumosinus dilatans, intra-orbital meningioma and neurofibromatosis type 2.