Objective: In this study our purpose was to demonstrate the differences of thorax, trachea and bronch diameters in the normal individuals and in the patients who have diffuse hyperaerated lungs.

Material and Method: We included 200 cases who had thorax CT scans for various reasons. A multislice CT scanner was used for the study. Diffuse hyperaeration was evaluated for each case's thorax CT. Our study group comprised 161 patients with bilateral diffuse hyperaeration while the control group comprised 39 patients without radiologically detectable hyperaeration . Density measurements were done for lungs accepting -910 HU and less as hyperaeration. Statistical analyses was applied to both groups for thorax AP / lateral diameters (thoracic index), trachea lateral /AP diameters (tracheal index), right main bronchus lateral/AP diameters and left main bronchus lateral/AP diameters (bronchial index) using SPSS 16.0. Mann-Whitney U test was used for comparison the two groups.

Results: There was significant discrepancy between two group's thoracic index, tracheal index and bronchial index measurements (p<0.05). ROC analysis showed that treshold value for thorax is 0,825. The patients with increased thorax AP diameters within the control group had higher median ages, concluding age has an effect on the increased thorax AP diameter.

Conclusion: Thoracic index is effected by hyperaeration. Hyperaeration cause saber sheath trachea configuration. Thoracic index values of 0.825 and higher favor increased thoracic AP diameter.