Magnetic resonance imaging (MRI) is a non-invasive method characterised by high temporal and spacial resolution that makes it possible to obtain very high-quality pictures. It is a less invasive method than TEE and is very significant in the diagnosis of heart tumours. MRI makes it possible to assess the parameters influencing hemodynamic as well as morphological qualities of the tumour such a its size, its movement, its relation to the surrounding structures and the presence of a capsule. With the use of additional programming, it is possible to evaluate, indirectly, the metabolism of the diagnosed lesion as well as the degree of blood perfusion. Thus, MRI diagnosis of the heart is a valuable complementary technique in the verification of the diagnosis and in the referral to cardiosurgical treatment. The aim of this paper is to present the use of MRI in the diagnosis of an abscess of the mitral valve anulus in a female patient who did not agree to the transoesophageal echocardiography (TEE). In this case, the usefulness of MRI to establish the diagnosis of the anular abscess of the mitral valve was proved. The final diagnosis was confirmed during the operation.