Peritoneal dialysis is a rare cause of pleural effusion. It appears, as a complication of continuous ambulatory peritoneal dialysis (CAPD), in approximately 2% of all CAPD patients. We describe three patients with pleural effusions secondary to CAPD. Because of the late onset of pleural effusion and pulmonary symptoms, i.e. months after CAPD treatment was initiated, the pleural effusion was not directly regarded as a complication of CAPD. After thoracocentesis with biochemical analysis of crystal clear pleural fluid and in two patients Tc-99 peritoneal scintigraphy/contrast enhanced CT-scanning, which demonstrated pleuroperitoneal communication, we concluded that pleural effusion was secondary to CAPD in these three subjects. All patients were treated with hemodialysis after cessation of CAPD and because two of them wanted to continue with CAPD, video-assisted thoracoscopic surgery with talc poudrage (chemical pleurodesis) was performed in order to prevent recurrence. Pleural effusions secondary to CAPD is not a frequent complication of CAPD though a very important one because CAPD must be stopped if it appears. Diagnostic thoracentesis (high glucose concentration) may be the simplest way to make a diagnosis but a contrast enhanced CT-scanning is essential for diagnosis of bigger diaphragmatic defects.