Tear size is a significant prognostic factor following rotator cuff repair. However, no study has investigated which dimension of the tear, the mediolateral or anteroposterior, more significantly influences the outcome when the product of the two dimensions, the tear size area, is similar. A retrospective cohort study was conducted with patients who underwent arthroscopic FTRCT repair. Two contrasting groups were derived from preoperative tear dimensions. The mediolateral dominant (MLD) group consisted of 45 FTRCTs with the mediolateral tear dimension at least 1.5 times larger than the anteroposterior, and retraction exceeding the humeral head apex. The anteroposterior dominant (APD) group included 35 FTRCTs with an inverse proportion of the dimensions and retraction short of the humeral head apex. Demographic data, pre- and postoperative magnetic resonance imaging (MRI), clinical scores, and strength were compared between the groups. The mean follow-up was 26.7 and 32.2 months in the MLD and APD groups, respectively. The tear size in area (MLD vs. APD, 521.0 vs. 523.4 mm2, P=.960) and the discrepancy between ML and AP dimensions (2.0 vs. 1.9, P=.597) were similar. However, the MLD group demonstrated significant female predominance (P=.003), dominant arm involvement (P=.007), a higher incidence of pathologic subacromial spurs (P=.016), narrower acromiohumeral distance (P<.001), shorter residual tendon (P<.001), and advanced supraspinatus muscle atrophy (P=.005). Other baseline parameters were comparable between the groups. At the one-year postoperative MRI, the MLD group demonstrated a significantly lower retear rate (4.4% vs. 31.4%, P=.001). Nevertheless, clinical scores and strength at the last follow-up did not significantly differ. In a similar tear size area, the greater AP width contributes more than the ML length in causing a retear. Female predominance, dominant arm involvement, subacromial spurs, shorter residual tendon, and supraspinatus muscle atrophy were more demonstrated in MLD tears. Surgeons should be aware that healing may be poor in APD tears despite less retraction.