Vascular malformations of the ventricular system are rare, and their clinical and radiologic characteristics vary depending on the location of the lesions. Many types are described, but a comprehensive summary is lacking. Herein, we add two cases to the literature and review known types of ventricular vascular malformations. One case involved a 37-year-old woman who presented with headache due to hydrocephalus. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a lesion of the foramen of Monro. The other case involved a 7-year-old boy who had dizziness and headache due to hydrocephalus. CT and MRI demonstrated a lesion of the third ventricle. In both cases, the images mimicked those of tumors with or without bleeding. As a result, the malformations were misdiagnosed, though surgical treatment was successful. In both cases, the lesions were proven to be arteriovenous malformations on pathologic evaluation. Correct diagnosis of ventricular vascular malformations is sometimes difficult but essential for good treatment planning. Their incidence is low. However, their bleeding and rebleeding rate is high, and they commonly cause hydrocephalus. Treatment should be timely and based on the type of lesion and its presentation.