BACKGROUND: Preprocedural cardiac magnetic resonance (CMR) imaging is crucial for identifying ventricular scar areas, borderline zones, and potential reentry channels. This study aimed to evaluate the impact of late gadolinium enhancement (LGE) core and borderline mass on the acute and long-term outcomes of ventricular tachycardia (VT) ablation in patients with structural heart disease (SHD). METHODS AND RESULTS: A total of 204 consecutive patients underwent CMR before scheduled VT ablation. Of these, 38 were excluded due to incomplete LGE quantification caused by device-related imaging artifacts, and 19 had no detectable left ventricular (LV) LGE, resulting in a final cohort of 147 patients with positive LGE (median age 64 years, 57% with non-ischemic cardiomyopathy [NICM], median left ventricular ejection fraction 38%, 61% with defibrillators). Patients with ischemic cardiomyopathy (ICM) had higher LV mass (86 vs. 75 g, P = 0.005) and LGE core mass (21 vs. 12 g, P = 0.001) compared to NICM patients, while borderline LGE mass was similar (2.9 vs. 2.5 g, P = 0.240). ICM patients more frequently presented with transmural inferior scars, whereas NICM patients exhibited more diffuse, non-transmural LGE patterns, particularly in the inferolateral, inferoseptal, and anteroseptal regions. Post-ablation, 28 patients (19%) remained acutely inducible (with clinical VT in two), and 53 patients (36%) experienced VT recurrence within a 20-month follow-up period. Neither high LGE core mass nor borderline mass predicted VT inducibility or recurrence. Most patients with clinical deterioration had NICM with septal involvement. CONCLUSION: In patients with SHD undergoing VT ablation, neither high LGE core mass nor borderline mass was predictive of postprocedural VT inducibility or recurrence.