Aims Currently, the ejection fraction [left ventricular ejection fraction (LVEF)] is the main criterion used for implanting implantable cardioverter defibrillators (ICDs) for primary prevention. However, many of ICD receivers would not have an event and do not have any gains from the device. Consequently, improving the discrimination strategies is needed. Here, we aimed at assessing the role of global longitudinal strain (GLS) for such purpose. Methods and results Seventy ischaemic or dilated cardiomyopathy cases characterized by LVEF ≤ 40% with a previously implanted ICD were enrolled. LVEF and GLS amounts were evaluated using 3D echocardiography. The occurrence of ventricular arrhythmias was checked by analysing the ICD history. Mean follow-up period of patients was 1.8 ± 0.6 years. There was a significant difference in the amount of GLS in arrhythmic cases compared with non-arrhythmic ones (À6.97 ± 3.06 vs À11.82 ± 4.25; P < 0.001). This difference was found in both ischaemic and dilated cardiomyopathy groups. A GLS below À10 cm/s could predict the occurrence of a ventricular event by 90% specificity and 72.2% sensitivity (area under the curve = 0.84, P < 0.001). While 27.39 (69.2%) patients with GLS below À10 cm/s had a ventricular event, only 3.31 (9.6%) of the patients with GLS above À10 had an event) P < 0.001). Those patients with a GLS ≥ 17 cm/s never experienced a ventricular arrhythmia. Conclusions Global longitudinal strain is a more accurate predictor of ventricular arrhythmias in patients with reduced LVEF. Whether it may help in selecting more appropriate patients for ICD implantation or not should be evaluated within a randomized trial in the future.