Percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) increases forward blood flow, possibly resulting in an increase in lumen diameter. We investigated the determinants of luminal gain at the distal reference segment following PCI for CTO. Forty-eight consecutive patients who underwent PCI for CTO were included in this study. Clinical and angiographic data were obtained at baseline and follow-up (mean follow-up period: 251 ± 73.6 days). Overall, the reference lumen diameter was 2.53 ± 0.38 mm at post-procedure and 2.38 ± 0.84 mm at follow-up. The distal reference lumen diameter (segment 5 mm distal to the stent) was larger at follow-up than at post-procedure (1.64 ± 0.64 and 1.38 ± 0.51 mm, respectively, P < 0.05). Luminal gain (LG), in the distal reference segment, defined as an increase in lumen diameter from post-procedure to follow-up, was observed in 33 of 48 patients (69%). Univariate and multivariate logistic regression analyses were performed to identify the clinical and angiographic predictors of LG. Minimum lumen diameter and left ventricular ejection fraction at baseline were both significant predictors of LG in univariate and multivariate logistic regression analyses. Luminal gain was observed at the distal reference segment following PCI for CTO. Left ventricular ejection fraction may have an impact on the lumen diameter distal to lesions responsible for CTO.