Coronary angiography is considered as the gold standard in the morphological representation of coronary artery stenosis. Coronary angiography is often performed without preprocedural non-invasive proof of ischemia and the assessment of the severity of a coronary lesion by morphology is very subjective. Thus, invasive fractional flow reserve (FFR) measurement represents the current standard for estimation of the hemodynamic relevance of coronary artery stenosis and facilitates decision making for percutaneous coronary intervention (PCI) and stenting. The FFR-guided revascularization strategy has been classified as a class IA recommendation in the 2014 ESC/EACTS guidelines on myocardial revascularization. Both the DEFER and the FAME studies showed no treatment advantage of hemodynamically irrelevant stenosis. By use of FFR (and targeted interventions), clinical results could be improved as well as the procedure costs were reduced; however, the use in clinical practice is still limited due to the need of adenosine administration and a significant prolongation of the procedure. Instantaneous wave-free ratio (iFR®) is a new innovative approach for the determination of the hemodynamic relevance of coronary stenosis which can be obtained at rest without the use of vasodilators. Regarding periprocedural complications as well as prognosis, iFR® showed non-inferiority compared to FFR in the SWEDEHEART and DEFINE-FLAIR trials.