Background/Objective: This study aimed to investigate the relationship between the pulmonary arterial computed tomography obstruction index ratio (CTOI) and the simplified pulmonary embolism severity index (sPESI), one of the clinical probability scoring modalities, in determining the severity of PE and to determine whether CTOI is a mortality marker. Methods: The study included 117 patients diagnosed with PE via computed tomography pulmonary angiography (CTPA). The CTOI was determined according to the localization of the embolus and the obstruction caused by the embolus in the vessel. Patients were divided into two groups, namely low-risk and high-risk groups, according to their sPESI values. Patient deaths up to six months after PE diagnosis were recorded. Results: According to the sPESI classification, although the CTOI was higher in the high-risk group compared to the low-risk group, no significant difference was found between the groups. The mortality rate was significantly higher in the high-risk group. After six months of follow-up, there was no difference in the CTOI rate between the patients who died and those who survived. Conclusions: Although CTPA is the gold standard for diagnosing PE, it would be more appropriate to use it together with clinical findings to determine the severity of the disease. Further evaluation is needed to investigate the usefulness of the obstruction index and CT findings of right ventricular dysfunction for classifying patient risk and determining therapeutic options.