Objective: Although several mucosal flap techniques have been reported to improve the outcomes in Draf IIb and Draf III procedures, there is scant knowledge on frontal ostium neo-osteogenesis after reconstruction with mucosa flap. This study evaluates the potential benefits of mucosa flaps on frontal ostium neo-osteogenesis after frontal sinus drill-out procedures. Methods: Forty-three patients who underwent extended Draf IIb and Draf III were enrolled. Among them, 20 patients had frontal neo-ostium (FNO) reconstructed by mucosal flap (group A), and 23 patients did not have neo-ostium reconstruction (group B). The cross-sectional area of FNO, frontonasal bone, and the amount of frontal neo-osteogenesis (FNOG) were measured with OsiriX (R). In addition, the Global Osteitis Scoring Scale (GOSS), Lund-Mackay score (LMS), and Lund-Kennedy score (LKS) were also evaluated. Results: At one year postoperatively, the remaining neo-ostium area was significantly larger in group A (p =.001), and group A had significantly less FNOG (p <.05). The month 12 postoperative GOSS score was significantly decreased in group A. In contrast, it slightly increased in group B. Both the average LKS and LMS were significantly reduced in groups A and B at month 12 postoperatively. Still, the average LKS of group A significantly decreased than that of group B at month 12 postoperatively. Conclusion: Coverage of the bare frontal bone with the mucosal flap could prevent excessive neo-osteogenesis and keep the neo-ostium open widely.