Purpose Whilst the pathophysiology of Pulmonary Embolus (PE) in major trauma patients is well described, less is understood about those presenting with a Pulmonary Thrombus (PT) on initial trauma CT scan, though direct thoracic trauma has been implicated. This study aims to compare the proportions of accepted risk factors for venous thromboembolic disease in patients with PT events versus both later PE events and a control group. Methodology This is a retrospective review of prospectively-collated trauma database of a major trauma centre, including all patients who had a PE during their admission from 2014-2023. events were categorised into ‘PE’ diagnosed <24 hours from admission (PT group), 24-72hrs (intermediate PE) and those diagnosed >72 hours for admission (late PE). Variables included patient demographics, anticoagulation and VTE history, shock, Injury Severity Score (ISS) and the Abbreviated Injury Score (AIS) for thoracic and head injury, and mortality. Analysis was two-fold, firstly a comparison the frequencies of co-variates between PT and late PE groups (Fischer’s exact & rank sum) and secondly, a case-control study where the PT group matched for age, gender, mechanism of injury and ISS with 3:1 with controls. Results 35 patients were included in the PT group and 129 patients in the late PE group. PT group patients were more likely to be female (37.3% vs 19.4%, p=0.02), however no other difference in age, mortality, ISS, thoracic or head AIS or admission details reached statistical significance. When compared to matched controls, the PT group were more likely to be smokers (OR 6.91 [1.63-33.65], p<0.05) and had a longer hospital length of stay (9.93 days vs 4.93, p<0.05) but no other differences reached statistical significance. Conclusion Trauma patients suffering a PT event are more likely to be female than later PE events, and smokers compared with controls. There was no evidence of an association with chest trauma in this series.