Background: Acute pulmonary embolism (PE) may result in right ventricular (RV) pressure overload with a dilated RV which can be diagnosed by two-dimensional echocardiography. Methods: A retrospective analysis was performed in 190 unselected patients who had acute PE documented by contrast-enhanced spiral computed tomographic scanning. The 190 patients included 104 women and 86 men, mean age 58 ± 15 years. Results: RV dilatation was present in 45 of 70 patients (64%) with bilateral PE, in 19 of 120 patients (16%) without bilateral PE, in 42 of 47 patients (89%) with main pulmonary artery embolism, in 34 of 84 patients (40%) with lobar PE, in 16 of 70 patients (23%) with segmental PE and in 6 of 36 patients (17%) with subsegmental PE; p < 0.001 comparing bilateral with no bilateral PE and main pulmonary artery embolism with no main pulmonary artery embolism, with lobar, segmental and subsegmental PE; p < 0.025 comparing lobar with segmental PE, and p < 0.02 comparing lobar with subsegmental PE. Conclusion: The prevalence of RV dilatation is highest in patients with main pulmonary artery embolism or bilateral pulmonary artery embolism; furthermore, the prevalence of RV dilatation is higher in patients with lobar PE than in patients with segmental or subsegmental PE.