[en] Correct diagnosis and prognostic assessment of cardiac masses are crucial before therapy. We evaluated the diagnostic and prognostic value of ${}^{18}$F-FDG PET/CT in patients with cardiac masses. ${}^{18}$F-FDG PET/CT images of 64 patients with 65 cardiac masses were retrospectively analysed (34 men, 30 women; average age, 51.2 ± 17.5 years). Comparisons of CT features and ${}^{18}$F-FDG metabolic indices between benign and malignant entities, as well as among primary and secondary malignancies and lymphoma, were performed. The diagnostic values of PET/CT for distinguishing benign versus malignant masses were calculated. PET/CT data were further assessed for the predictive value for overall survival (OS) using the Cox proportional hazards model to assess potential independent predictors. Kaplan-Meier curves were generated to assess the value of PET/CT for prognostication. Statistically significant differences in various morphological features and metabolic indices between benign and malignant masses were found. An SUV${}_{max}$ of 6.75 was the optimal cutoff value to differentiate between benign and malignant masses, and the diagnostic sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were 92.11%, 88.89%, 90.77%, 92.11%, and 88.89%, respectively. Taking CT features and SUV${}_{max}$ ≥ 6.75 as a criterion, the values were 76.32%, 100.00%, 86.15%, 100.00%, and 75.00%, respectively; taking ≥ 3 CT features or SUV${}_{max}$ ≥ 6.75 as a criterion, the values were 94.74%, 88.89%, 92.31%, 92.31%, and 92.31%, respectively, indicating optimal diagnostic performance when paired with the anatomic information provided by the CT component. A univariate analysis of OS determined that surrounding tissue infiltration, epicardial infiltration, necrosis, multiple chambers or vessel involvement, distant metastasis, SUV${}_{max}$, SUV${}_{mean}$, metabolic tumour volume (MTV), and total lesion glycolysis (TLG) were significant predictors of survival. In the multivariate analysis, only SUV${}_{max}$ ≥ 6.715 was significant (P < 0.01). Median OS was 1460 days for SUV${}_{max}$< 6.715 and 342 days for SUV${}_{max}$ ≥ 6.715 (P < 0.01). ${}^{18}$F-FDG PET/CT is helpful in the diagnosis of cardiac masses before treatment and has value in detecting extracardiac primary or secondary tumours. ${}^{18}$F-FDG PET/CT could also be a promising tool to provide prognostic information for these patients, especially SUV${}_{max}$ displaying independent prognostic value.