PURPOSE: Iliac vein compression is a known culprit of deep vein thrombosis (DVT). In contrast, the compression may prevent the pulmonary embolism (PE). The aim of this study was to evaluate the anatomic and clinical risk factors of PE in patients with lower extremity DVT. METHODS: PE was evaluated using chest computed tomography in patients with lower extremity DVT. The patients were classified into group I (DVT without PE) and group II (DVT with PE) and analyzed to clarify the anatomic and clinical risk factors associated with PE in patients with DVT. As the anatomic factor, the shortest length between the common iliac artery (CIA) and spinal body (SB) was measured. Statistical analyses utilized the multivariable logistic regression model, and receiver operating characteristic (ROC) curve analysis. RESULTS: We examined 114 patients (age; 62.7 ± 16.9 years, 41.7% men) with DVT with/without PE. The prevalence of concurrent DVT with PE was 52.6%. Blood tests showed no difference between the 2 groups. Of all the assessed patients' characteristics, only infection was significantly and independently associated with PE (P = 0.04). The shortest length between CIA and SB was 6.7 ± 3.5 mm in group I and 11.3 ± 3.7 mm in group II (P < 0.001). ROC curve analysis showed that 7.6 mm was the cut-off value for the anatomic risk of PE. CONCLUSION: Infection was significantly associated with concurrent DVT and PE. The shortest length between CIA and SB (<7.6 mm) may prevent PE in patients with DVT.