Slow flow or no-reflow is a serious complication during percutaneous coronary intervention (PCI), but little is known about the risk factors. A 64-year-old man underwent coronary angiography and PCI for stable angina. Pre-interventional intravascular ultrasound demonstrated an ultrasound attenuated coronary plaque, as a long eccentric bulky plaque with a marked decrease of the back echo without calcification. Since the lesion was highly eccentric in the large left anterior descending artery, directional coronary atherectomy (DCA) and subsequent stent implantation were planned. Serious no-reflow occurred after DCA. The DCA specimen suggested that the lipid-laden atheromatous gruel could attenuate the ultrasound reflection and cause distal embolization, resulting in no-reflow during PCI. The presence of ultrasound attenuated coronary plaque is a predictor of slow flow or no-reflow in PCI, indicating that distal protection devices may be required during the procedure.