Vascular birthmarks are common lesions that can be divided into hemangiomas and vascular malformations (arterial, venous, capillary, and lymphatic malformations or a combination of these), according to Mulliken. Thirty-four patients with a vascular malformation were evaluated prospectively with magnetic resonance imaging (MRI) during a 6-year period in a combined study of the departments of radiology and plastic and reconstructive surgery. Hemangiomas were not part of this study, as they regress spontaneously in childhood. MRI and angiographic findings are described and the value of MRI is investigated for its usefulness in conjunction with angiography. MRI turns out to be superior as the initial diagnostic test for vascular malformations. Further investigations are not necessary in low-flow lesions. In case of high-flow and combined-flow lesions, angiography is indicated following MRI to show the exact angioarchitecture, which is essential for therapy planning. A flowchart, based on radiodiagnostic features, is proposed for diagnostic evaluation of patients with vascular birthmarks.