The purpose of our study was to investigate the clinical relevance of a pseudofilling defect in the left atrial appendage (LAA) detected on coronary computed tomography (CT) angiography (CCTA) as an indicator of impaired left atrial (LA) volumetric function in patients with chronic atrial fibrillation (CAF).Forty-two patients with CAF underwent CCTA. Quantitative and visual measurements of contrast enhancement of the LAA were performed, and they were correlated with results of CT volumetric functional analysis of the LA. Four volumetric parameters representing LA function were measured: maximum (LAVmax) and minimum volumes of the LA (LAVmin) through the entire cardiac cycle; LA emptying volume (LAEV); and LA emptying fraction (LAEF). All volumetric parameters were standardized by body surface area to adjust for variation in LA size among patients. For quantitative measurement, the CT attenuation was measured at the LAA and the LA to calculate an LAA/LA attenuation ratio. For visual measurement, contrast enhancement of the LAA was categorized into 3 groups; no filling defect, mild-to-moderate pseudofilling defect, and severe pseudofilling defect group. The Spearman correlation coefficient and the Kruskal-Wallis test were used for statistical analysis.The LAA/LA ratio showed a strong positive correlation with LAEV (r = 0.52; P < 0.001) and LAEF (r = 0.69; P < 0.001). The LAEV in the no pseudofilling defect group and the mild-to-moderate and severe pseudofilling defect groups were 16.1 ± 8.4, 10.8 ± 3.1, and 6.7 ± 4.9 mL/m², respectively (P < 0.001). The LAEF in each group were 24.2 ± 13.8%, 12.0 ± 3.4%, and 6.9 ± 3.1%, respectively (P < 0.001).The severity of pseudofilling defect in the LAA on CCTA could predict the degree of LA emptying dysfunction in patients with CAF.