The frontal sinus of 47 adult half-head cadaveric specimens were observed. The case of the sinus opening into nasal cavity directly through the ostia are 30 to frontal recess, 9 to ethmoidal infundibulum, 3 to superior semilunar hiatus and superior meatus, respectively. Only 4 (8.5%) cases are directly opened into the nasofrontal duct. The adjacent structures of the ostia differ from each other by the different location of the ostium. The clinical significance of the ostium and the nasofrontal duct were discussed.