BACKGROUND: To evaluate the characteristics of brain arteriovenous malformations (AVMs) with coexisting flow-related and Willis circle aneurysms. METHODS: The 302 consecutive retrospectively reviewed patients from the Beijing Tiantan Hospital were analyzed in this study. The presence of cerebral aneurysms was confirmed by pretreatment selective and superselective angiography. Univariate and multivariate analyses were performed for patient age, sex, history of rupture, associated aneurysms, AVM size, and deep and superficial venous drainage. RESULTS: Of the 302 patients, 41 (13.6%) had AVMs associated with intranidal aneurysms, and 33 (10.9%) had AVMs associated with extranidal aneurysms. Of the 33 patients, 24 (72.7%) had a flow-related and 9 (27.3%) had a Willis circle aneurysm. Flow-related and Willis circle aneurysms correlated positively with intracranial hemorrhage (P = 0.003), patient age (P = 0.003), and infratentorial AVMs (P = 0.040) in multiple univariate analysis. CONCLUSIONS: Flow-related and Willis circle aneurysms coexisting with cerebral AVMs frequently are associated with initial hemorrhage presentation, patient age, and infratentorial AVM location.