Aims: Bioabsorbable polymer drug-eluting stents (DES) may reduce the inflammation and delayed healing associated with some permanent polymer-coated DES. Whether late clinical outcomes are improved, particularly among patients with medically treated diabetes, is unknown. Therefore, we analysed outcomes from a pre-specified substudy of the EVOLVE II trial to evaluate the safety and effectiveness of the SYNERGY stent in patients with diabetes mellitus. Methods and results: SYNERGY is a thin-strut, platinum-chromium everolimus-eluting stent with an ultra-thin bioabsorbable poly(DL-lactide-co-glycolide) abluminal polymer. The EVOLVE II randomised, controlled trial proved the non-inferiority of the SYNERGY versus the PROMUS Element Plus stent for one-year target lesion failure (TLF: ischaemia-driven target lesion revascularisation [ID-TLR], target vessel myocardial infarction [TVMI], or cardiac death). The pre-specified EVOLVE II diabetes substudy prospectively pooled randomised patients with diabetes (N=263) with a sequential single-arm diabetic cohort (n=203). The substudy primary endpoint was one-year TLF compared with a pre-specified performance goal (14.5%). The primary endpoint occurred in 7.5% of SYNERGY-treated patients with diabetes, significantly less than the performance goal (p<0.0001). The two-year rate of TLF was 11.2% (cardiac death 1.5%, TVMI 6.4%, ID-TLR 6.8%) and definite/probable stent thrombosis occurred in 1.1% of patients. Conclusions: The EVOLVE II diabetes substudy demonstrates the efficacy and safety of the SYNERGY stent in patients with medically treated diabetes. Clinical Trial Registration Information: NCT01665053 (http://clinicaltrials.gov/).