The authors summarize current data demonstrating how the excellent spatial resolution of CT-QCT, improved tissue characterization, and multi-energy capabilities expand the diagnostic potential of cardiac CT. Applications include accurate detection and quantification of coronary artery calcification, assessment of coronary plaque burden and composition, improved evaluation of coronary stents, and comprehensive myocardial tissue characterization and perfusion analysis. By providing high-quality spectral information and detailed tissue characterization, CT-QCT represents a noninvasive alternative for assessing coronary artery disease and myocardial pathology, reducing the need for invasive coronary angiography and cardiac MRI. Despite remaining challenges in technology and clinical application, CT-QCT has the potential to revolutionize cardiovascular diagnostics, streamline diagnostic workflows, and improve patient care through more accurate, optimized, and comprehensive assessment.