Background. If, when and how to treat patients with chronic ischemic mitral regurgitation remains at present controversial. An encouraging surgical approach is represented by performing under-sized mitral annuloplasty in most part of patients with mitral regurgitation due to annular dilation or papillary muscle displacement. However, the modifications at mid-term follow-up of the diastolic function in these patients, hasn’t been definitely established yet. So, in this study we focused on the functional results observed in patients who underwent undersized mitral annuloplasty, paying particular attention to diastolic function. Methods. We retrospectively investigated all available data from 112 patients affected by chronic ischemic mitral regurgitation who underwent surgical myocardial revascularization associated to implantation of a prosthetic (mitral) annular ring. Mean follow-up time was 20 ± 10 months Results. Mitral repair was possible in every patient, 30-day mortality was 5.4%. The strongest associations with hospital mortality at univariate analysis were a poor ejection fraction (p = 0.002) and an high pulmonary pressure (p = 0.001). At late follow-up no residual regurgitation was present in 71% of patients, trivial regurgitation in 24% and mild in 5%. Tenting area reduced from 3.4 ± 1.1 cm2 to 1.9 ± 0.5cm2 at discharge (p<0.001), and to 1.9 ± 0.5cm2 and 1.9 ± 0.3cm2 at early and late follow-up. Systolic and diastolic sphericity index significantly reduced at discharge (p = 0.002 and p < 0.001, respectively) and at early follow-up (p < 0.001). Considering at least a 15% decrease of the end-systolic volume of the left ventricle as an index of left ventricular reverse remodelling (LVRR), 61% of the patients (n. = 64) showed LVRR at discharge, 78% (n. = 61) at early follow u3p (χ^2 = 10.1, p = 0.006) and 87.5% (n. = 79) at late follow-up (χ^2 = 0.57, p = ns). Part of the patients recovered a normal diastolic pattern at discharge (46%), at early follow-up (50%) and at late follow-up (54%). Conclusions. Adding an undersized annular ring implantation to complete myocardial revascularization yields to good functional results in terms of freedom from mitral regurgitation recidivism, reverse left ventricular remodelling, and improvement of both systolic and diastolic left ventricular function.