To prospectively assess clinical benefits of fractional flow reserve (FFR) in guiding coronary artery bypass grafting (CABG).GRAFFITI is a single-blinded prospective multicenter randomized controlled trial for FFR-guided versus angiography-guided CABG. We enrolled patients, undergoing coronary angiography, having significantly diseased left anterior descending or left main stem and at least one more major coronary artery with intermediate stenosis, assessed by FFR. Surgical strategy was defined based on angiogram, blinded to FFR values prior to randomization. After randomization, patients were either operated following the angiogram-based strategy (Angiography-guided group) or according to FFR: i.e. with FFR≤0.80 as cut-off for grafting (FFR-guided group). Primary endpoint was graft patency at 12 months. Trial was registered (NCT01810224). Between March 2012 and December 2016, 172 patients were randomized either to angiography-guided (84 patients) or to FFR-guided group (88 patients). Patients had median of 3 [3;4] lesions. Diameter stenosis was 65% [50%;80%], FFR was 0.72 [0.50;0.82]. Compared to angiography-guided group, FFR-guided group received less anastomoses (3 [3;3] vs. 2 [2;3] respectively; p=0.004). One-year angiographic follow-up showed no difference in overall graft patency (126 [80%] vs 113 [81%], respectively; p=0.885). One-year clinical follow-up, available in 98% of patients, showed no difference in composite of death, myocardial infarction, target vessel revascularization and stroke.FFR-guidance of CABG has no impact on 1-year graft patency, but it is associated with a simplified surgical procedure.