Abstract: Objective: To investigate the diagnostic value of dual-source CT (DSCT) in evaluating adults with atrial septal defect (ASD) with pulmonary hypertension (PAH). Methods: Seventy-five adult patients with ASD in our hospital were retrospectively analyzed. The study sample was divided into 2 groups (PAH group (n=40) and non-PAH group (n=35 cases)) according to the mean pulmonary artery pressure (mPAP) obtained by right cardiac catheterization (RHC) (PAH: ≥ 25 mmHg). All patients were examined for congenital heart disease by DSCT one week before RHC. The ascending aorta diameter (AAD), main pulmonary artery diameter (MPAD), right pulmonary artery diameter (RPAD), left pulmonary artery diameter (LPAD), right lower pulmonary artery diameter (RLPAD), the maximum diameter of the short axis of both the ventricles (RVD, LVD), included the angle of the spinal ventricular septum and ASD diameter, were measured on the image. The MPAD to AAD ratio (rPA) and the RVD to LVD ratio (RVD/LVD) were calculated. Differences between the two groups in terms of clinical data, RHC indexes, and CT cardiovascular parameters were evaluated by a t-test. The ROC curve was used to determine the diagnostic efficacy of DSCT in adults with ASD and PAH. Pearson correlation coefficient was used to analyze the association between the CT parameters, mPAP, and PVR. Results: The statistically significant CT indexes between the two groups were MPAD, RPAD, LPAD, RLPAD, RVD including the angle of the spinal ventricular septum, rPA, RVD/LVD, and ASD diameter. Of these, the RPAD and LPAD including the angle of the spinal ventricular septum, rPA, RVD/LVD, and ASD diameter demonstrated moderate diagnostic efficacy for PAH (AUC>0.7). The MPAD, rPA, and ASD diameter with mPAP were moderately positively correlated. The MPAD, rPA, and RVD/LVD with PVR were also mildly positively correlated. Furthermore, the ASD diameter and PVR were highly positively correlated. Conclusion: DSCT is diagnostically valuable for the evaluation of adults with ASD complicated with PAH. In particular, DSCT may be used to provide a comprehensive evaluation before clinical treatment, as well as for long-term follow-up and management.