In the year 2005, 10 public health care institutions in Lodz contained general surgery units. The lowest mortality rate, 0,35%, was recorded in the surgical unit of University Teaching Hospital No. 5 (UH No. 5). We performed a retrospective comparative analysis of mortality in this hospital and in the two remaining university teaching hospitals, University Teaching Hospital No. 1 (UH No. 1) and University Teaching Hospital No. 2 (UH No. 2). The study was comprised of data from 18911 patients treated in these units from 01.01.2003 to 31.12.2005. The statistical data were collected by the Provincial Centre of Public Health in Lodz. The structure of the analysed units and the structure of the selected groups of diagnoses were compared. A relative structure similarity index was used to compare the structure of hospitalised patients in the analysed units, in an attempt to discover the reasons for significantly lower mortality among patients hospitalised in surgical unit of UH No. 5. A detailed analysis of the selected diagnoses and of mortality indicated that early postoperative intensive care in severely ill patients and immediate admission to the ICU, when indicated, significantly decrease mortality.