BACKGROUND AND OBJECTIVES: Tinnitus is a common disorder, but the etiology of this disorder remains unknown. The objective of this study was to assess the correlation between anatomical type and the thickness of the anterior inferior cerebellar artery (AICA) loop with tinnitus, using 3D-fast imaging employing steady state acquisition magnetic resonance image (MRI). MATERIALS AND METHODS: 74 patients with tinnitus and 82 asymptomatic controls were included in this study. Otologic symptoms, which was measured based on the results of a pure tone audiometry, were reviewed. We evaluated the position and thickness of the AICA vascular loop in 3D-FIESTA MRI using two scoring systems. The first system was Chavda classification based on the anatomical location of the AICA loop. The second scoring system was used to measure the thickness of the AICA loop. The AICA loops were classified into two groups based on thickness, thinner than adjacent facial nerve and thicker than the facial nerve. RESULTS: Ears with type I, II AICA loops showed significantly higher rates of tinnitus than those with type III. There was no association between the type of AICA loop and subtype of tinnitus (pulsatile, nonpulsatile). There was no association between the type of tinnitus and hearing loss. Ears with thinner AICA loop had a higher rate of tinnitus than those with thicker AICA loop. CONCLUSIONS: The type I, II and thinner AICA loop was significantly correlated with tinnitus. Compression of VIIIth cranial nerve by AICA loops at a cerebellopontine angle and impaired blood flow through the vessel may be the pathophysiology of tinnitus.