Objective To explore the clinical value of 18F-FDG PET/CT in differentiating between cardiac benign and malignant lesions. Methods From September 2009 to September 2012, a total of 9 (7 males, 2 females, average age (46±22) years) patients with space-occupying lesions of the heart underwent whole body 18F-FDG PET/CT. 18F-FDG PET/CT diagnosis was made according to morphologic features and SUVmax of lesions. The final diagnoses were confirmed by either histopathology or clinical data and follow-up. Two-sample t test was used for data analysis. Results Among 9 cases of cardiac occupying lesions, 4 cases were malignant tumors, 4 cases were benign tumors (including 2 lipomas, 1 myxoma, and 1 fibroma), 1 case was thrombus. The average SUVmax of malignant tumors was 18.99±14.58, which was significantly higher than that of benign tumors (2.35±1.46, t=-2.58, P<0.05). With a cut-off SUVmax of 4.6, 18F-FDG PET/CT could be used to noninvasively detect malignant tumors with a sensitivity of 4/4, specificity of 4/5, and accuracy of 8/9. Only 1 thrombus was misdiagnosed. Conclusion 18F-FDG PET/CT can aid the noninvasive differential diagnosis of cardiac malignant tumors from benign lesions. Key words: Heart neoplasms; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose