A 62-year-old man was admitted to our hospital with acute myocardial infarction. An emergent coronary angiogram-revealed two severe stenoses in the proximal and middle part of the LAD. Initially, stent implantation to the mid-lesion was performed under distal protection with an occlusion balloon (GuardWire Plus). Subsequently, stent implantation to the proximal lesion was performed similarly, but this time we located the occlusion balloon at just distal of the prior stent to protect a distal diagonal branch. After the second stent implantation, acute occlusion occurred at the prior stent. On IVUS findings, the prior stent was found shortened and distorted, which seemed to be the cause of acute occlusion. We demonstrated that an inflated occlusion balloon could shorten and distort stents in in vitro experiments. Close attention is necessary in cases of multiple stent implantations under distal protection.