Accurate assessment of aetiology of mitral regurgitation (MR) is one of the key steps in the decision-making process and further clinical management of patients with severe MR. Our clinical case illustrates the added value of three-dimensional echocardiography (3DE) in assessment of mitral valve morphology and identification of an unexpected mechanism of MR which was not previously diagnosed using conventional echocardiography. 3DE helped to choose appropriate management strategy in this patient. We believe our observations may have an important clinical impact, encouraging a wider use of 3DE in patients with complex mechanisms of MR