Hepatic hydrothorax is defined as the presence, in a cirrhotic patient, of a large pleural effusion in the absence of primary pulmonary or cardiac disease. Pleural effusions occur in 5% to 10% of patients with cirrhosis of the liver. The effusions are usually right-sided, but may be bilateral or left-sided. The precise mechanism of fluid accumulation is not clear. We reported a case of right hepatic hydrothorax occuring in the liver cirrhosis with ascites. Diagnosis was confirmed by the intraperitoneal and intrapleural injection of radioisotope $^{99m}Tc-tin$ colloid that demonstrated the one-way transdiaphragmatic flow of fluid from the peritoneal to pleural cavities.