목적: To evaluate the prevalence of anterior ethmoid artery (AEA) below the level of base of skulls in Thais and to determine the relationship between AEA and bullar lamella/anterior wall of ethmoid bulla (BL/AWEB) and vertical ground lamelle (GL) of middle turbinate (MT) 방법:100 consecutive patients had undergone CT of PNS. Relevant images included those of axial CT with contiguous 1 mm thickness and similar contiguous thickness images in coronal and sagittal planes were reconstructed. Entrance and exit points of each AEA in ethmoid sinus were determined by a consensus of a rhinologist and one head and neck radiologist.Locations of AEAs in relation to skull base were assessed independently by two assessors (experienced rhinologist and experienced radiologist). Consensus opinion was made unless there was disagreement and, of importance were distances between AEA and skull base, between AEA and BL/AWEB, and between AEA and GL of MT. In this study, measurements were made as exactly as possible by means of ruler icon in the Dicom system. 결과:Hanging AEAs below skull base was found to be 72.5%. Mean distance (MD)between AEA and skull base was 3.2 mm. In 81.3% of cases, AEAs exited the ethmoid sinus through lateral lamella of cribriform plate and through fovea ethmoidalis in 18.7%. Interestingly, AEAs usually ran anteromedial in 94.5% and horizontal in 5.5 %. Nearly all AEAs i.e. 95.0%were located between EB and GL, 95.0% and only 5% was at or behind GL. Having used mid-points to divide distances between EBs and GLs into anterior and posterior halves(PHs), AEAs were located in PHs in 71.0%, 69.1% located in at the entrance and 75.0% at the exit. 결론:Most AEAs were found to be below skull base and mostly were present posterior to the mid-point of the distances between BL/AWEB and vertical GL of middle turbinate. Bullar lamella /AWEB and vertical GL of middle turbinate are two constant anatomic landmarks of importance that otorhinolaryngologists should use in attempting to locate AEAs.