A 56-year-old female with chronic renal failure caused by chronic glomerulonephritis underwent continuous ambulatory peritoneal dialysis(CAPD)in December 2005. Approximately 3 months later, a large right hydrothorax suddenly developed. The concentration of glucose in the intrapleural fluid was markedly higher than that in serum, suggesting pleuroperitoneal communication. Technetium-99m-labeled macroaggregated albumin scan clearly demonstrated communication between the peritoneal and pleural cavities. Despite the condition, the patient wanted to continue with CAPD and thus video-assisted thoracoscopic surgery was performed. Using dialysis solution containing indigo carmine infused through a CAPD catheter, we found two blebs on the diaphragm that gradually became enlarged and stained blue. Dialysis solution flowed through one of these blebs. Following cyst removal, the diaphragm defect was directly closed with a surgical stapler. The postoperative course was very favorable and the patient could restart CAPD the day following surgery, and was discharged from our hospital on day 7 postoperatively. Two years and 10 months since the surgery, there has not been any recurrence of hydrothorax.