Congenital ventricular diverticulum (CVD) in adults is a rare cardiac malformation, which includes fibrous type congenital ventricular aneurysm (CVA). CVA is often clinically asymptomatic and shows no abnormality in the electrocardiogram or chest X-ray. However, some cases of sudden death resulting from ventricular tachycardia, cardiac embolism or ventricular rupture have been reported. Therefore, physicians should perform further cardiac imaging studies to detect a CVA if ventricular arrhythmia originating from the left ventricle is observed. Here, we report two successfully followed cases of CVA which were diagnosed from premature ventricular contractions.