Objective: This article aims at evaluating the effectiveness of abduction and external rotation (ABER) position used in magnetic resonance (MR) arthrography for diagnosing rotator cuff tears. Methods: A retrospective analysis was performed using 183 MR arthrography images of shoulder joint. Each patient was either examined in a neutral position or ABER position. Then the imaging results were compared with those diagnostic results obtained from shoulder arthroscopy. Also the specificity, sensitivity, negative predictive value, positive predictive value, and accuracy of MR arthrography in the two positions described above were evaluated. Results: A total of 64 patients were diagnosed with rotator cuff tears using arthroscopy and the diagnostic results include 16 complete rotator cuff tears and 48 partial tears; 47 supraspinatus tendon tears and 17 posterosuperior cuff tears; 22 delamination tears and 26 tears complicated with anteroinferior labrumeligament complex injuries. The differences in specificity, sensitivity, negative predictive value, positive predictive value and accuracy between neutral position and ABER position using MR arthrography were not statistically significant (all P > 0.05). For diagnosing posterosuperior cuff tears, the sensitivity of ABER position was significantly higher than that of the neutral position (94.12% vs. 64.71%, P = 0.034). For diagnosing delamination tears, the sensitivity and negative predictive value of ABER position were significantly higher than those of the neutral position (P = 0.009 and P = 0.036 respectively). For diagnosing rotator cuff tears complicated with anteroinferior labrumeligament complex injuries, the sensitivity of ABER position was statistically higher than that of the neutral position (96.15% vs. 73.08%, P = 0.021). Conclusion: This study suggests that MR arthrography in ABER position is a superior tool for diagnosing certain types of rotator cuff tears. Apart from that, MR arthrography in ABER position improved the detection rate of posterosuperior cuff tears, delamination tears and rotator cuff tears complicated with anteroinferior labrumeligament complex injuries. (C) 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.