Objective: To compare the incidence of pulmonary embolism (PE) in cancer and non-cancer patients with lower extremity deep vein thrombosis (DVT). Methods: The clinical data of 128 patients with lower extremity DVT admitted in recent years were retrospectively analyzed. The patients were divided into cancer group (16 cases) and non-cancer group (112 cases), and the incidences of symptomatic PE between the two groups during hospitalization and follow-up period were compared, respectively. Results: During hospitalization (7–14 d), the incidence of symptomatic PE in cancer group and non-cancer group was 25.0% and 2.7% respectively, and the difference had statistical significance (P=0.005). During follow-up period (6–60 months), two cases in cancer group and 8 cases in non-cancer group were lost to follow-up, and one case in each group developed PE (8.3% vs. 0.89%) and died, and the difference had no statistical significance (P=0.185). Conclusion: The incidence of PE is increased in cancer patients with lower extremity DVT.