OBJECTIVES: To clarify the possible pathological conditions of cartilaginous portion of the Eustachian tube (ET) and its surrounding tissues. STUDY DESIGN: Retrospective review. PATIENTS: Twenty-five normal subjects (control group) and 25 patients with patulous ET (patulous group). METHODS: We reconstructed cross-sectional 3 Tesla magnetic resonance (MR) images using the multiplanar reconstruction (MPR) technique. Cross-section area widths that were measured included the following: 1) inferior head of lateral pterygoid muscle (PM); 2) pterygoid venous plexus (PVP); 3) medial soft tissues of ET, including ET cartilage; and 4) maximum cross-sectional area of high intensity surrounding the medial ET lumen. RESULTS: A statistically significant difference was found in the thickness of the inferior head of the lateral PM between male and female; it was thicker in the male participants. Ostmann's fatty tissue (OF) was significantly smaller in the patulous ET group. CONCLUSION: Smaller size of the surrounding tissues of the ET, viz., the OF, may contribute to the pathogenesis of patulous ET.