BACKGROUND: This study aimed to comparatively evaluate the morphological and morphometric characteristics of the right atrial appendage (RAA) and left atrial appendage (LAA) in the same individuals using multidetector computed tomography (CT) and to investigate age- and sex-related differences. MATERIALS AND METHODS: Pulmonary multidetector CT angiography images of 300 patients (167 women, 133 men; mean age, 54.0 ± 15.9 years) without pathological findings were retrospectively evaluated to assess the morphological and morphometric characteristics of both atrial appendages. Detailed morphometric measurements, including appendage length, width, orifice dimensions, orifice area, and volume, were performed for the RAA and LAA in each individual. RAA and LAA measurements were compared, and age- and sex-based analyses were performed. Interobserver agreement was assessed using kappa statistics. RESULTS: The most common RAA morphologies were sailboat (triangular) (48.3%) and horsehead (quadrangular) (25%), whereas the most frequent LAA types were chicken wing (55.7%) and windsock (20%). All morphometric parameters, including length, width, orifice dimensions, orifice area, and volume, were significantly greater in the RAA than in the LAA (all p < 0.001). No significant sex-related differences were observed for any RAA or LAA measurements. Age-based analysis revealed no significant changes in RAA parameters; however, LAA width (p = 0.002), orifice length (p = 0.027), orifice area (p = 0.031), and volume (p = 0.036) increased significantly, particularly in individuals older than 65 years. Interobserver agreement was excellent for all measurements. CONCLUSIONS: The RAA has significantly larger morphometric dimensions than the LAA in the same individuals and does not appear to be affected by age or sex. In contrast, several LAA parameters show age-related increases. These distinct morphometric differences provide clinically relevant anatomical reference data and may have important implications for interventional planning and the assessment of atrial appendage-related pathologies.