Background and Objectives: Selection of the appropriate stent diameter may be important during percutaneous coronary intervention (PCI) for preventing late stent thrombosis. We evaluated the predictors for changes in reference vessel diameter (RVD) in patients with coronary artery disease (CAD). Subjects and Methods: 1,081 patients (1,688 lesions) with complete quantitative coronary angiographic data before and after PCI were analyzed retrospectively. We calculated the % change in RVD as following equation: RVD after PCI / RVD before PCI x 100(%). We defined constricted coronary artery (CCA) when the % change in RVD was 110% or more, a 75th percentile value of % change in RVD. The subjects were divided into two groups according to the presence or absence of CCA. Results: Percentile change in RVD was 103% (101-106%) in 789 patients (1,266 lesions) without CCA and 117% (113-123%) in 289 patients (422 lesions) with CCA. Baseline characteristics and initial laboratory findings were not different between two groups. The rate of acute myocardial infarction, initial vital sign and Killip classification were similar. Elective PCI was frequent in non-CCA group (77.4% vs. 71.3%, p=0.04). Lesion location and severity were not different. In CCA group, the rate of chronic total occlusion (CTO) (3.3% vs. 7.3%, p<0.01), infarct-related artery (IRA) (14.4% vs. 19.0%, p=0.24) and initial TIMI flow grade 0 or 1 (18.1% vs. 28.4%, p<0.01) were significantly higher but rate of moderate to severe calcification (29.0% vs. 22.2%, p=0.01) was lower. Lesion length was longer in CCA group (24.9짹8.3mm vs. 26.1짹9.2mm, p=0.01). In univariate analysis, presence of CTO [odd ratio (OR) 2.3; 95% confidence interval (CI): 1.4-3.7], initial TIMI flow grade 0 or 1 (OR 1.8; 95% CI: 1.4-2.3), IRA (OR 1.4; 95% CI: 1.0–1.9) and calcification (OR 0.7; 95% CI: 0.5–0.9) and lesion length (OR 1.02; 95%CI: 1.00-1.03) was associated with CCA. Conclusions: The acutely or chronically occluded diffuse coronary artery lesions with less calcification are associated with higher changes in RVD between pre-PCI and post-PCI.