<b><i>Objective:</i></b> The aim of this study is to determine whether sex and age influence posterior semicircular canal (PSC) thickness. <b><i>Methods:</i></b> This observational study was conducted in 3 tertiary hospitals. The minimal distance between the PSC and the posterior cranial fossa (PSC thickness) was estimated by thin-section multidetector row computed axial tomography (CAT) scan of the temporal bones. Nonselected consecutive patients of all ages (607 temporal bones) were considered. <b><i>Results:</i></b> A significant effect was only detected for sex (<i>F</i> = 5.418, <i>p</i> = 0.020); PSC thickness showed a higher mean value in women (mean difference ± SE: 0.224 ± 0.096 mm). A significant and negative <i>r</i> value was detected for males aged >45 years (-0.173, <i>p</i> = 0.026); in that group of patients, PSC thickness decreased as age increased (0.018 ± 0.008 mm/year). For females aged ≤45 years, a significant and positive <i>r</i> value was found (0.198, <i>p</i> = 0.022); in that group, PSC thickness increased as age increased (0.020 ± 0.008 mm/year). <b><i>Conclusions:</i></b> PSC thickness did not significantly evolve with age in young males (≤45 years) but it decreased from age 45 years onwards. On the other hand, PCS thickness increased with age in women until the age of 45 years and it did not significantly change in older females.