Background: Alpha V beta 3 (αvβ3) is an integrin specifically expressed on the endothelial cells of central nervous system (CNS) neoplasms. However, no data exist on the expression of αvβ3 in vascular malformations of the CNS. In this study, we investigate the expression of αvβ3 in arteriovenous malformations (AVMs) and cavernous malformations (CMs). Method: Frozen samples of AVMs from 12 patients and CMs from 5 patients were obtained intraoperatively. Once the final pathology had been confirmed, immunohistochemistry was performed using an antibody to the integrin αvβ3. The αvβ3 expression pattern was graded according to the percentage of positively staining vessels. Results: Ten of 12 AVMs demonstrated αvβ3 immunopositivity. Six of these 10 AVMs had moderate or strong staining. Most notably, 5 of the 6 moderate or strongly staining AVMs came from patients 22 years of age or younger. Four of these 6 AVMs had previously been embolized. None of the cavernous malformations demonstrated αvβ3 immunopositivity. Discussion: αvβ3 may contribute to the formation of AVMs in younger patients. αvβ3 may also provide a potential therapeutic target. The lack of αvβ3 expression in cavernous malformations, despite their high vascular densities, suggests that the pathophysiology of their formation differs from that of AVMs.