Background: In ST-segment-elevation myocardial infarction (STEMI), cardiovascular magnetic resonance (CMR) holds the potentiality to improve risk stratification beyond Thrombolysis-in-Myocardial-Infarction (TIMI) risk-score. Nevertheless, the optimal timing for CMR after STEMI remains poorly defined. Objectives: Comparing prognostic performance of three different stratification strategies according to the timing of CMR after STEMI. Methods: The population of this prospective registry-based study included 511 reperfused STEMI patients. All patients underwent post-reperfusion (median:4-days post-STEMI) and follow-up (median:4.8-months post-STEMI) CMR. Left ventricular (LV) volumes, function, infarct-size and microvascular-obstruction extent (MVO) were quantified. Primary end-point was a composite of all-death and heart failure (HF) hospitalization.Three multivariate models were developed including TIMI risk-score plus early post-STEMI (early-CMR) or follow-up CMR (deferred-CMR) or both CMRs parameters along with adverse LV remodeling (paired-CMRs). Results: During a median follow-up of 8.5 years, primary end-point occurred in 85 patients (23 deaths; 38 HF hospitalization). Early-CMR, deferred-CMR and paired-CMRs demonstrated similar predictive value for primary end-point (C-statistic: 0.726, 0.728, 0.738, respectively; P=0.663). However, early-CMR enabled to correctly estimate poor outcome in 4 of 7 patients (56%) developing primary end-point between early- and deferred-CMR. Conclusions: In STEMI, early-CMR should be considered the preferred strategy for timely effective risk stratification.