Chylopericardium refers to existing communication between the pericardial sac and the thoracic duct carrying the chyle. The objective of our report was to highlight the specificity of diagnosis and treatment of this rare but tedious condition through the analysis of two case reports. Male patient, aged 63 years, with chylopericardium was diagnosed perioperatively (implantation of artificial aortic--St. Jude No 21 and mitral valve--St. Jude No 29). Etiology of pericardial effusion was established by Sudan III staining of punctate specimen obtained by subxiphoid pericardial puncture. Probable cause of chylopericardium was the lesion of ductus thoracicus during cross-clamping of the superior caval vein with a Cooley clamp. Initial treatment included diet rich in medium-chain triglycerides which resulted in resolution of the effusion. During five-year follow-up, there were no recurrences of pericardial effusion. The second patient was female, 21 years old, with chylopericardium after partial pericardiectomy performed because of the chronic severely symptomatic pericardial effusion, resistant to other forms of treatment. Pericardiocentesis provided 650 ml of yellowish fluid with a high concentration of cholesterol (3.2 mmol/l), triglycerides (16.6 mmol/l), and proteins (64.7 g/l), which verified chylopericardium, most probably as a consequence of the lesion of ductus thoracicus during partial pericardiectomy. Diet rich in medium-chain triglycerides failed to decrease the effusion, after two weeks of treatment (daily secretion 250-350 ml). Lymphography revealed lesion of ductus thoracicus, most probably at Th9/Th10 level, with no direct visualization of extravasal accumulation of contrast media. Surgical ligation of ductus thoracicus was performed through the right thoracotomy. However, postoperative secretion increased to 1000 ml/day. Patient underwent redo surgery comprising the ligation of lymphatic vessels, guided by extravasation of intraoperatively iwected methylene-blue indicator. During one-year follow-up, there were no recurrences of pericardial effusion. In conclusion, intraoperative lymphography significantly contributed to successful surgical treatment of patients with chylopericardium.