OBJECTIVES: To determine the prevalence of frontoethmoidal cells (FECs) in patients with and without frontal sinus/recess mucosal thickening and to establish the relationship between the FECs and the frontal sinus/recess mucosal thickening. MATERIALS AND METHODS: We retrospectively reviewed 245 consecutive ostiomeatal CT scans (490 sides). The normal and frontal sinus/recess mucosal thickening groups were categorized based on these images. The latter group was sub-categorized into the frontal sinus mucosal thickening group (FS group) and the frontal recess mucosal thickening group (FR group). RESULTS: Types 1, 2, 3 and 4 frontal cells were found in 17.5, 6.7, 8.3 and 0% of 326 normal sides, respectively. The prevalence of agger nasi, suprabullar, frontal bullar, supraorbital ethmoid and interfrontal sinus septal cells was 85.6, 43.3, 4.9, 4.3 and 17.2% of the same 326 normal sides, respectively. Type 3 frontal cells, frontal bullar cells and suprabullar cells were more prevalent in the FS and FR groups than in the normal group. All types of cells were more prevalent in the FS group, but only the suprabullar cells were more prevalent in the FR group than in the normal group. CONCLUSION: These findings suggest that type 3 frontal cells, frontal bullar cells and suprabullar cells may have a significant association with frontal sinus/recess mucosal thickening.