Persistent left superior vena cava (PLSVC) is the most common anomaly of systemic venous return. Its occurrence is found in 0,3 to 0,5 % in general population and even up to 10 % in patients with congenital heart defects. We presented a patient with numerous cardiological burdens who has been admitted to our clinic for implantation of cardiac resynchronization therapy with defibrillator (CRT-D) due to heart failure (NYHA III class) with accompanying permanent atrial fibrillation and left bundle branch block with QRS width of 160 ms. During the implantation in venography we found PLSVC. Despite this anomaly, we found one big lateral branch for introduction of leads and the procedure was successful. PLSVC is usually asymptomatic and found accidentally, just like in our patient. Unfortunately, the existence of PLSVC significally worsens the prognosis of patients undergoing implantation. In case of failure, the only solution remains cardiac surgery.