Objectives: Pulmonary hypertension (PH) is a progressive, potentially fatal disease, difficult to diagnose early due to non-specific nature of symptoms. PH is associated with increased morbidity and death in many respiratory and cardiac disorders, and with all-cause mortality, independent of age and cardiopulmonary disease. The main pulmonary artery diameter (MPA), and ratio of MPA to adjacent ascending aorta (AA), MPA:AA, on Chest CT are strong indicators of suspected PH. Our goal was to determine the prevalence of abnormally high values of these indicators of PH in asymptomatic low-dose CT (LDCT) screening participants at risk of lung cancer, and determine the associated risk factors. Methods: We reviewed consecutive baseline LDCT scans of 1949 smokers in an IRB-approved study. We measured the MPA and AA diameter and calculated MPA:AA ratio. We defined abnormally high values as being more than two standard deviations above the average (MPA >= 34 mm and MPA:AA >= 1.0). Regression analyses were used to identify risk factors and CT findings of participants associated with high values. Results: The prevalence of MPA >= 34 mm and MPA:AA >= 1.0 was 4.2% and 6.9%, respectively. Multivariable regression demonstrated that BMI was a significant risk factor, both for MPA >= 34 mm (OR = 1.07, p < 0.0001) and MPA:AA >= 1.0 (OR = 1.04, p = 0.003). Emphysema was significant in the univariate but not in the multivariate analysis. Conclusions: We determined that the possible prevalence of PH as defined by abnormally high values of MPA and of MPA:AA was greater than previously described in the general population and that pulmonary consultation be recommended for these participants, in view of the significance of PH.