To summarize the performance of CT-based main pulmonary artery diameter or pulmonary artery to aorta ratio (PA:A ratio) measurement in detection of pulmonary hypertension by a systematic review and meta-analysis. A comprehensive literature search was performed to identify studies determining diagnostic accuracy of main pulmonary artery diameter or PA:A ratio measurement for pulmonary hypertension. The Quality Assessment of Diagnostic Accuracy Studies tool was used to assess the quality of the included studies. A bivariate random-effects model was used to pool sensitivity, specificity, positive/negative likelihood ratio (PLR/NLR), and diagnostic odds ratio (DOR). Summary receiver operating characteristic (SROC) curves and area under the curve (AUC) were used to summarize overall diagnostic performance. This meta-analysis included 20 publications involving 2134 subjects. Summary estimates for main pulmonary artery diameter measurement in the diagnosis of pulmonary hypertension were as follows: sensitivity, 0.79 (95% CI 0.72-0.84); specificity, 0.83 (95% CI 0.75-0.89); PLR, 4.68 (95% CI 3.13-6.99); NLR, 0.26 (95% CI 0.20-0.33); DOR, 18.13 (95% CI 10.87-30.24); and AUC 0.87. The corresponding summary performance estimates for using the PA:A ratio were as follows: sensitivity, 0.74 (95% CI 0.66-0.80); specificity, 0.81 (95% CI 0.74-0.86); PLR, 3.83 (95% CI, 2.70-5.43); NLR, 0.33 (95% CI 0.24-0.44); DOR, 11.77 (95% CI 6.60-21.00); and AUC 0.84. Both main pulmonary artery diameter and PA:A ratio are helpful for diagnosing pulmonary hypertension. Nevertheless, the results of pulmonary artery measurement should be interpreted in parallel with the results of traditional tests such as echocardiography.