Objective To investigate the relationships between parameters of frontal ostium and morphological parameters of agger nasi cell and the severity of chronic frontal sinusitis(CFS).Methods Retrospective analysis was performed to 25 patients with normal sinuses (control group) and 113 CFS patients (CFS group). According to the soft tissue density rate (STDR,%), all the subjects in both groups were subdivided into subgroups of 0, 1, 2, 3 and 4 points. Their computerized tomography data were used for three-dimensional reconstruction of frontal sinus and agger nasi cell, and relevant parameters were measured. The Kruskal-wallis test was used to analyze the relationships between parameters of frontal ostium and morphological parameters of agger nasi cell and the severity of CFS.Results ①Morphological parameters of the agger nasi cell were not identical in the five groups of patients with different degrees of frontal sinus turbidity. The volume, surface area, and vertical diameter of the agger nasi cell of group 0 were lower than those of the other groups, and the differences were statistically significant (P<0.05); the mediolateral dimension of the agger nasi cell of group 0 were lower than those of groups 1 and 3, and the differences were statistically significant (P<0.05).②The parameters of frontal ostium were not identical in the five groups of patients with different degrees of frontal sinus turbidity. The anterior-to-posterior (A-P) length of the isthmus of normal group 0 was higher than the rest of the groups, and the FI cross-sectional area of group 0 was higher than that of groups 2, 3 and 4, with statistically significant differences (P<0.05). The FI value and FI cross-sectional area of group 1 were higher than those of groups 3 and 4, with statistically significant differences (P<0.05), and the FI cross-sectional area of group 2 was higher than that of group 4, with statistically significant differences (P<0.05). The higher the degree of frontal sinus turbidity, the smaller the FI and FI cross-sectional area compared with the normal 0 group.③Spearman rank correlation analysis suggests that:FI cross-sectional area was positively correlated with FI and FR values (r_s=0.606, r_s=0.213, P<0.05) and weakly negatively correlated with the volume, surface area and vertical diameter of the nasal nasi cell (r_s=-0.154, r_s=-0.161, r_s=-0.250, P<0.05). The volume of the nasal nasi cell was weakly negatively correlated with FI (r_s=-0.276, P<0.05).Conclusion Morphological parameters of the agger nasi cell and FI value and FI cross-sectional area are involved in the occurrence and development of CFS, and are negatively correlated with the severity of CFS.