Legal opinions in the area of internal medicine, opinionated by the Forensic Medicine Department, Medical University of Lódź, Poland in 2002, were selected for further analysis and assessment in the course of medical treatment. During this period opinions were given in 20 cases, most of which concerned cardiovascular, secondly respiratory, followed by, endocrine diseases. In half of the cases analyzed it was determined that medical treatment had been incorrect. All of the objectionable diagnostic and therapeutic procedures evidenced some form of decisional error. In most cases errors were made in the diagnosis, as a result of neglect in performing necessary examinations, or of erroneous interpretation of results obtained.