<p><strong>Background</strong>: Out-of-hospital cardiac arrest (OHCA) is a leading cause of death and is regarded as a significant public health issue. Immediate treatment with an automated external defibrillator (AED) increases OHCA patient survival potential. For AEDs to be used and fulfil their lifesaving potential, they need to be in close proximity to the victim and accessible at the time of a cardiac arrest. The current paper sheds light upon an optimized location-allocation method achieving full coverage with immediate accessibility in an urban context given a limited number of available AEDs for deployment using GIS. The case study is the Region of Western Macedonia (RWM) in Greece for a pilot AED placement program for the Governance of RWM. The focus of the current study is the capital city of RWM, Kozani. The initial number of the defibrillators (120) that are needed to be distributed is very small and cannot cover the needs for every major city or rural area in the region. Out of the 120 AEDs, the challenge is to find the minimum required number of AEDs to allocate in the city providing full coverage and accessibility. This paper focuses only on one city, however, the same methodology was applied to allocate AEDs in the other selected cities of the region. The rural dimension and methodology are not in the scope of this paper. <br> <strong>Methods</strong>: Road network data, spatio-temporal analysis of accessibility network, digital elevation model, land uses, population density, seasonal fluctuations and socio-demographic variables were used. GIS algorithms such as spatial analysis, kernel density, hot spot analysis, maximal covering location problem (MCLP) tests, proximity algorithms, buffer zoning, were a few of the tests made in order to find the most efficient positions and maximize coverage keeping in mind that access to an AED until defibrillation time must not exceed the time range of five minutes. <br> <strong>Results</strong>: optimised sites and allocated AEDs in urban areas we managed to achieve full city coverage with 17 AEDs. In every part of the city, people can have access to a nearby AED with its critical radius of less than or equal to 250m achieving defibrillation in the critical period of 5 minutes. The results are promising for the establishment and expansion of optimised AED deployment in cities. <br> <strong>Conclusions</strong>: The progress of the project must be monitored and there are still unresolved problems that need to be tackled to provide a robust allocation of future defibrillators. Further research to enhance our understanding on public access defibrillation and optimize the accessibility and functionality of the medical health care services is needed. A network of engaged and informed citizens ready to act is required for a successful public access defibrillation program.</p>