Knowledge and training of staff who encounter life-threatening patients in their daily work is vital. Continuous transfer of knowledge and experience is needed for nurses / technicians who very often find themselves working alone with a patient whose life is in danger. It is, therefore, necessary to constantly supplement them with new knowledge and renew their previously acquired skills. In emergency medical activities limited resources – such as scarcity of time and diagnostic and therapeutic means – are constantly present. In the work of emergency medical care there are several unfavourable factors that make it difficult to work in such special settings. Basic life support (BLS) in cardiopulmonary resuscitation (CPR) is usually used only as an auxiliary method of maintaining ventilation and circulation, until the arrival of the fully equipped team. Chest compressions are the most important part of BLS. The aim of this thesis was to investigate the impact of bystander practice of heart massage on the result of cardiopulmonary resuscitation in the outpatient emergency medical service in Zagreb County area, as well as to determine the frequency of certain variables, analyse the results of cardiopulmonary resuscitation with respect to return of spontaneous circulation (ROSC) and investigate the relationship of the variables we collected with outcomes. For the purposes of acquiring and analysing the data, the Utstein form was used, which is an internationally accepted standard for cardiopulmonary performance reporting resuscitation. Data from all Utstein forms from the Department for emergency medicine of Zagreb County were retrospectively analysed in the period from January 1 2020 to January 1 2021. Demographic data and characteristics of cardiopulmonary resuscitation / outcome were analysed, with respect to the return of spontaneous circulation. The results obtained from this research can be used for planning of further education of both lay individuals and health professionals, as well as planning the network of automated external defibrillators. The research was conducted in accordance with ethical principles and the Protection Act personal data.