Coronary computed tomography angiography (CCTA) and CT-derived fractional flow reserve (FFRCT) findings demonstrate high diagnostic accuracy, aligning consistently with invasive coronary angiography (ICA), the gold standard diagnostic technique for coronary artery disease. The differential diagnosis of total versus subtotal coronary occlusion is crucial in determining the appropriate treatment strategy. Subtotal coronary occlusions composed of vulnerable tissue can sometimes present as total coronary occlusions on ICA. This presentation can be inconsistent with findings from CCTA and FFRCT. This case report presents discrepant findings between CCTA, which indicated subtotal coronary occlusion, and ICA, which suggested total coronary occlusion. The stenotic lesion, filled with vulnerable tissue (low-attenuation plaque volume: 20.3 mm3 and intermediate-attenuation plaque volume: 71.6 mm3), could be dilated with a vasodilator during maximal hyperemia. This dilation facilitated the acquisition of CCTA and FFRCT images. We were able to diagnose subtotal coronary occlusion and identify the overall anatomical structure of the vessels prior to percutaneous coronary intervention (PCI). This allowed us to perform a successful and uncomplicated PCI.