- Background Collateral coronary flow may protect patients against myocardial ischemia. There is no data regarding the difference in collateral development in relationship to coronary dominance and potential influence on outcome. We aimed to investigate whether there is a relationship between coronary dominance, collateral development and influence on outcome. Methods The study population comprised all patients with single vessel disease and right or left coronary dominance (RD or LD), with a proximal stenosis above 90%. Demographic, clinical and angiographic data were compared in patients with RD and LD, as well as outcome. Results More patients with ST elevation myocardial infarction (STEMI) and RD demonstrated collaterals compared to LD (51% vs. 26%, p = 0.042) and had a higher Rentrop score (1.5 ± 0.6 vs. 1.0 ± 0, p < 0.05). Fewer patients died in the RD group (9% vs. 26% in the LD group, p = 0.018). In patients without STEMI, there was a tendency to more collateral development in the RD group (although this difference became significant in patients with totally occluded vessels 80% in RD vs. 57% in LD, p < 0.05). In addition, in this group of patients without STEMI, (as in the STEMI group), there were fewer deaths in the RD group over the study period (6% vs 18% in the LD group, p < 0.01). Conclusions Patients with single vessel disease and RD develop more collaterals than those with LD, and have a better outcome. In addition, in individuals with STEMI and single vessel disease with collaterals, those with RD have a higher Rentrop score.