Background: Primary or secondary malignancies of the heart is rare and difficult to diagnosis. Most cardiac masses are detected incidentally. Positron emission tomography-computed tomography, thorax computed tomography are valuable tools for staging the disease of patient with a history of malignancy. As prognosis is poor, if a physician suspects a suspicious metastasis on heart, it must evaluated carefully in order to prompt therapeutic interventions. Herein. we report a false-positive positron emission tomography-computed tomography finding which was superposition of lung metastasis of prostate adenocarcinoma via confirming by thorax computed tomography and echocardiography. Case report: A 71-year-old man diagnosed with prostate adenocarcinoma presented with a mass on the posterior-anterior lung graphy after 8 years of the diagnosis date. Positron emission tomography-computed tomography, thorax computed tomography, echocardiography, fine needle aspiration biopsies were performed in order to reveal the final diagnose. Although positron emission tomography-computed tomography revealed a cardiac metastasis, the other tools showed that it was not cardiac metastasis but lung metastasis of prostate adenocarcinoma.: Conclusion: A patient with a history of malignancy and clinical cardiac symptoms must be evaluated carefully in order to prevent a false-positive findings and to prompt therapeutic interventions.