Aim. Presentation of the difficulties in diagnosing Munchausen syndrome by proxy. Method. Comparison of four different conclusions in forensic psychiatric opinions issued in one case, due to the need of answering to the questions of the court, in what periods and why was the deterioration of the child's health, in connection with an allegation that the mother has acted to his detriment. In the first medical-legal opinion the treating physician, while being the head of the ward and the person informing the police of the action against a child by the mother, recognised Munchausen syndrome by proxy. The second opinion was delivered by a psychologist, who stated that the mother distinguished the introspective attitude characterised by excessive, exaggerated accuracy, thoroughness, and did not give a unambiguous answer to the questions of the court. In the third opinion the experts accepted that the functioning of the subject does not create a threat to life and health of the child. The fourth opinion developed by the authors of this paper noted that in the analysed medical records of the childs' hospitalisation, no arguments were found to recognise Munchausen syndrome by proxy. Results. In the conducted extended ambulant study of the subject and the analysis of the medical documentation of the 31 hospitalisations of the child showed that the improvement of the child's health was not associated in exclusion of pushing aside the mother from the child, but was the result of the consistency of the therapeutic treatment team, the continuation and the modification of the treatment. Conclusions. In appointing the expert, the art. 196 of the Code of Criminal Procedure should be considered, which states that the expert should not be the treating doctor, because his opinion loses value impartiality. Diagnosis of Munchausen Syndrome by proxy itself stirs up numerous controversies..