Background and Aims: There is no study in the literature that investigates an asymmetric morphological feature of the frontal sinus (FS). Materials and Methods: Four hundred and sixty-nine consecutive direct X-rays of FSs were analyzed for the asymmetry between the right and left sides. When an asymmetry in the height and contour of the FS existed, this difference was quantified. Results: Of the 469 patients, X-rays of 402 patients (85.7%), there was an asymmetry between right and left sides of the FS. Of these 235 (50.1%) were dominant on the left side, whereas 167 (35.6%) were dominant on the right, the sinuses of remaining 67 patients (14.3%) was symmetric. Statistical Analysis: The comparisons between parameters were performed using Wilkinson signed rank test. The relationship between handedness and sinus asymmetrywas also examined by two proportions test. There is statistically significant difference between the dominance of left and right FS. Conclusions: Hemispheric dominance may have some effect (s) of on sinus asymmetry of the human cranium. Surgeons sometimes enter the cranium through the FS and knowledge of asymmetric FS is important to minimize surgical complications.