Background and ObjectivesZZThe anatomy surrounding the frontal sinus (FS) and the anterior ethmoid artery (AEA) is variable and complex. We tried to determine the value of AEA as a landmark for finding FS during endoscopic sinus surgery. Subjects and MethodZZUsing the high-resolution CT scans of coronal and sagittal reconstruction, the distance between AEA and FS (D-AF) and the number and type of intervening cells between these two structures were investigated. Next, the distance between AEA and the anterior skull base (D-AS) was measured and the correlation between D-AF and D-AS was analyzed. ResultsZZA total of 119 nasal cavities from 70 subjects was analyzed. Of these analyzed, AEA was located just behind the frontal recess in only 17 nasal cavities (14%) and one or two intervening cells were located between FS and AEA in the remaining 86% of the nasal cavities. The most frequent type of intervening cells was supra bullar cell, followed by supraorbital and frontal bullar cells. The mean D-AF and D-AS measurements were 8.58±5.56 mm (0-22.6 mm) and 1.65±1.90 mm (0-6.7 mm), respectively. D-AS was not significantly correlated with the dis tance between the FS and AEA (p=0.433), therefore, D-AS could not be predicted. ConclusionZZThe relationship between FS and AEA was non-predictable, and in most cases, there were one or two intervening cells between FS and AEA. Therefore a thorough review of thin section CT scans is necessary. Korean J Otorhinolaryngol-Head Neck Surg 2014;57(10):687-91 Key WordsZZComputed tomography ㆍEndoscope ㆍEthmoid ㆍFrontal sinus ㆍParanasal sinus.