AIMS: To explore possible associations that may explain the greater benefit from cardiac resynchronization therapy (CRT) reported amongst women. METHODS AND RESULTS: In an individual-patient data meta-analysis of five randomized controlled trials, all-cause mortality and the composite of all-cause mortality or first hospitalization for heart failure (HF) were compared among 794 women and 2702 men assigned to CRT or a control group. Multivariable analyses were performed to assess the impact of sex, QRS duration, HF aetiology, left ventricular end-diastolic diameter (LVEDD), and height on outcome. Women were shorter, had smaller LVEDD, more often left bundle branch block, and less often ischaemic heart disease, but QRS duration was similar between sexes. Women tended to obtain greater benefit from CRT but sex was not an independent predictor of either outcome. For all-cause mortality, QRS duration was the only independent predictor of CRT benefit. For the composite outcome, height and QRS duration, but not sex, were independent predictors of CRT benefit. Further analysis suggested increasing benefit with increasing QRS duration amongst shorter patients, of whom a great proportion were women. CONCLUSIONS: In this individual-patient data meta-analysis, CRT benefit was greater in shorter patients, which may explain reports of enhanced CRT benefit among women. Further analyses are required to determine whether recommendations on the QRS threshold for CRT should be adjusted for height. (ClinicalTrials.gov numbers: NCT00170300, NCT00271154, NCT00251251).