Venous and arteriovenous malformations (VMs and AVMs, respectively) are rare vascular malformations that affect veins and arteriovenous connections, respectively. Both malformations can be diagnosed by clinical and histological examinations. Most of these malformations are sporadic; however, there may be cases of inherited malformations. Genetic testing is important to identify the molecular cause and establish the recurrence risk in families. Genetic testing should also be used because drugs that target specific proteins or pathways may be used for patients with known mutations in order to give more focused treatments. In those kinds of malformations, PI3K/AKT/mTOR and RAS/MAPK pathways are hyperactivated (as in tumors); therefore, inhibitors of those pathways can be found among drugs used in cancer therapies. Patients with VMs and AVMs should always be subject to genetic testing for the identification of the molecular cause (associated gene, somatic or germline mutation, recurrence risk) in order to identify the most appropriate drug for treatment.