Introduction. Patient aggression affects healthcare quality and, in extreme situations, may even lead to medical malpractice. Little is known, however, about the specific distribution of health care professionals’ exposure to patient aggression in various countries. Objective. The aim of this study was to assess the exposure of various professional groups of healthcare personnel to patient aggression, and to identify potential determinants (medical profession, age, gender, professional experience and employment at outpatient/inpatient healthcare units) of this exposure. Methods. The study was performed between January 2008 – December 2009 in northeastern Poland, and included 1,624 healthcare workers (493 nurses, 504 midwives, 501 physicians and 126 medical rescue workers). Exposure to eight forms of patient aggression was assessed using the MDM Mobbing Questionnaire. Results. Using a raised voice was the most frequently observed form of aggression in all groups, whereas the least frequent form of aggression encountered was the use of direct physical violence. In inpatient healthcare units, the intensity of patient aggression was encountered most by nurses and medical rescue workers, followed by physicians and midwives. In outpatient healthcare units, medical rescue workers experienced significantly higher levels of aggression when compared to other professional groups. Significant differences in mean aggression intensity experienced in inpatient and outpatient healthcare units were observed only in nurses and physicians. Furthermore, no significant effects of gender were observed on the intensity of patient aggression. Conclusion. Nurses are most exposed to different forms of patient aggression, with verbal attacks being most prevalent. Nurses employed at inpatient healthcare units experienced aggression more frequently than those working in outpatient healthcare units.