Background and aim of the study: The study aim wasto determine the impact of prosthesis-patientmismatch (PPM) on early and late clinical outcomes,left atrial and ventricular remodeling, late tricuspidvalve regurgitation and pulmonary hypertension(PH) in patients after mitral valve replacement(MVR).Methods: A total of 46 patients (mean age 66 ± 9.3years) with mitral valve diseases and undergoingisolated MVR was enrolled in the study. The mitralvalve effective orifice area (EOA) was determinedusing the continuity equation and indexed for thepatient’s body surface area (EOAi). PPM was definedas EOAi ≤1.2 cm2/m2. PH was defined as a systolicpulmonary artery pressure (sPAP) >40 mmHg. Both,clinical and echocardiographic follow up wereperformed.Results: PPM was identified in 25% of patients, butno significant differences were observed in baselineand operative characteristics when comparingpatients with and without PPM. The NYHA classwas improved in most cases after surgery. Indeed,significant decreases in mean transvalvular gradient(from 8.6 ± 2.8 mmHg to 5 ± 1.3 mmHg, p = 0.001),left atrial dimension (LAD) (from 31.9 ± 9.8 mm to29.5 ± 7 mm, p = 0.011), left ventricular end-systolicdiameter (from 42.6 ± 18.1 mm to 35.5 ± 6.6 mm,p = 0.044) and left ventricular end-diastolic diameter(from 55.8 ± 19.2 mm to 48.7 ± 6.1 mm, p = 0.024) wereobserved over time when comparing preoperativeand postoperative echocardiographic data. Inaddition, at follow up (mean 6.9 ± 1.8 years) therewere significant decreases in LAD (from 31.9 ± 9.8mm to 28 ± 11.1 mm, p = 0.001), left ventricular enddiastolicvolume (from 106.9 ± 32.9 ml to 92.3 ± 21.9ml, p = 0.024), tricuspid regurgitation (TR) (from 87%to 27%, p = 0.002) and PH (from 78.3% to 58.7%,p = 0.043) in all patients. No significant differenceswere observed in hemodynamic, clinical outcomeand atrial natriuretic peptide levels of patients withand without PPM.Conclusion: Mitral PPM does not appear to have anynegative effect on ventricular and atrial remodeling,TR and PH during the early and late postoperativeperiods.