Background and aim of the study: Blood cysts of cardiac valves are generally seen in newborns and infants and very rarely in adults. Although in most cases they are incidental findings they may be associated to severe cardiac or systemic complications. This study analyzes incidence, presentation and treatment of valvular blood cysts in adults. Methods: A review of the pertinent literature through a search mainly on PubMed and Medline was performed. Results: In patients ≥ 18 years of age, our search disclosed 54 patients with mitral blood cysts (mean age, 48±18 years), 9 with a tricuspid valve cyst (mean age, 67±15 years), 3 with a blood cyst on the pulmonary valve (age 31, 43 and 44 years) and 1 aortic valve cyst in a 22-year-old man. Most patients were asymptomatic while stroke, syncope or myocardial infarction occurred in 6 patients with a mitral valve cyst. Blood cysts were removed surgically in 70% of patients with a mitral cyst, in 55% with a tricuspid cyst and in all those with a pulmonary or aortic cyst. At histology the cyst wall was composed mainly by fibrous tissue and with the inner surface lined with typical endothelium. Conclusions: Blood cysts of cardiac valves are rare in adults but may cause life-threatening complications particularly when located on the mitral valve. For such reason surgical removal appears advisable, with low-risk procedures. Widespread use of multimodality imaging techniques will most likely increase the number of valvular blood cysts diagnosed also in adults.