Purpose <p>The objective of this study was to explore the relationship between a quantitative CT analysis and the expression of programmed death-ligand 1 (PD-L1) in lung adenocarcinoma.</p> Materials and methods <p>This study included 116 patients diagnosed with lung adenocarcinoma who were assessed for the expression of PD-L1. Tumors were classified as pure ground-glass nodules (GGNs), part-solid nodules, and solid nodules. The quantitative CT analysis included the tumor diameter and volume, solid component diameter and volume, and rate of the solid components. The CT criteria, and PD-L1 expression rates were compared based on the tumor proportion score (TPS). Optimal cutoff values were obtained utilizing the maximized Youden index method based on the receiver operating characteristic (ROC) analysis. Univariate and multiple linear regression analyses were also performed to examine the influencing factors of 50% and 1% PD-L1 expression.</p> Results <p>Solid nodules were significantly more frequent in the TPS ≥ 50% group (TPS ≥ 50% = 81.8% vs. TPS &lt; 1% = 10.0%). The rate of solid component diameter and rate of solid component volume were significantly smaller in TPS &lt; 1% than in TPS &lt; 50% and 1–49% (p &lt; 0.001, respectively). Multiple linear regression analysis identified the rate of solid component volume as a significant factor influencing 50% and 1% PD-L1 expression (p &lt; 0.001 and p = 0.048, respectively).</p> Conclusion <p>High PD-L1 expression rates may be associated with higher rates of solid components in lung adenocarcinoma.</p>