Two young adult males presented with paranasal sinus osteoma associated with mucocele. A 20-yearold man presented with headache and seizure, and another 20-year-old man presented with headache, frontal deformity, and visual disturbances. Both patients underwent surgery and satisfactory results were obtained. Isolated paranasal sinus osteomas are benign and slow-growing tumors, but may become more aggressive in association with mucoceles. The higher aggressiveness of the lesions may be due to the presence of the mucocele. Calcification and ossification of the mucocele probably contributes to the unexpected enlargement of the osteoma.