Objectives: To evaluate magnetic resonance imaging (MRI) findings in vascular malformations by assessing (1) the prevalence of phleboliths and flow voids and (2) dynamic contrast enhancement characteristics in early and delayed contrast phases. Methods: Ninety-eight patients (median age 27 years) were included. MRI analyses were performed by 2 radiologists that were blinded to clinical information. Phleboliths and flow-voids were assessed with T1 and short tau inversion recovery. Artery-lesion enhancement time (ALET) was assessed with time-resolved MRI angiography. Contrast accumulation until 15 minutes postinjection was assessed using subtraction techniques based on volumetric interpolated breath-hold examination. Standard statistical methods were applied. Results: Eighty-nine patients had low-flow malformations and 9 patients had high-flow malformations. Phleboliths were present in 13.5% of low-flow malformations, and 0% of high-flow malformations (P = .60). Flow voids were observed in 16.9% of low-flow malformations and 55.6% of high-flow malformations (P < .05). Median ALET of low-flow malformations was 9.2 seconds and of high-flow malformations (n = 8) was 0.8 seconds (P < .05). Twenty-one low-flow malformations had ALET that overlapped with ALET of high-flow malformations (≤6.3 seconds). Contrast accumulation between preinjection and 2 minutes postinjection was observed in 97.5% of low-flow malformations and 100% of high-flow malformations, whereas contrast accumulation between 2 and 15 minutes postinjection was observed in 92.6% of low-flow malformations and 62.5% of high-flow malformations (P < .05). Conclusion: Our data suggest that phleboliths are infrequent in vascular malformations and that flow voids may be unreliable markers of high-flow malformations. Both high- and low-flow malformations may present with considerable overlap regarding flow dynamics, implying vascular heterogeneity within both malformation types.