Background: Persistent left superior vena cava (PLS VC) is the most common thoracic venous anomaly.Hypothesis: This study examines the epidemiologic, clinical, and morphologic characteristics of a cohort of patients with PLSVC draining into the coronary sinus.Methods: We examined the clinical and morphologic characteristics of patients with PLSVC draining into the coronary sinus diagnosed at a single referral hospital for a defined population in northwestern Spain. We designed a prospective study of the case records of all patients diagnosed with PLSVC draining into the coronary sinus at the echocardiog‐raphy laboratory of the Hospital Xeral‐Calde from January 2001 through December 2002. Patients were included if they had a PLSVC diagnosed by transthoracic echocardiogram (TTE) using an echo‐contrast enhancement and confirmed by a magnetic resonance (MR) imaging. Ten patients (6 women) fulfilled the inclusion criteria described above. All patients were adults and had associated heart disease, including a congenital heart disease in three cases.Results: Magnetic resonance imaging examination confirmed the presence of PLSVC and the site of drainage into the coronary sinus. Absence of the right superior vena cava was observed only in three patients, in whom the main coronary sinus size was significantly increased. Absence of the left bra‐chiocephalic vein was diagnosed in five patients.Conclusion: This study describes 10 new cases of PLSVC and supports the necessity of considering PLSVC draining into the coronary sinus in the diagnosis of patients presenting with dilated coronary sinus diagnosed by TTE. It also underlines the important role of MR imaging in the evaluation of these abnormalities. An associated heart disease must always be excluded in these patients.