Seismic hazard analysis of vulnerable countries on the Alpine-Himalayan belt has great importance to be considered. Recently, Iran as one of the countries located on the stated belt has experienced a few number of severe earthquakes. A wellestablished index of how earthquakes affect buildings is by assessing probable Peak Ground Acceleration (PGA) which can be estimated by past events. For this reason, taking into account active faults around a city, and extracting seismic catalogues to categorize effects of surrounding faults on seismicity of the cities is a crucial step. The mentioned catalogues must be refined in both time and space to increase statistical independency of strong ground motion data, subsequently. There are two different approaches in estimation of PGA in seismic design of structures. Deterministic approach is unable to consider all characteristics of a site; however, the probabilistic hazard assessment which has been extensively used in recent years, applies a number of distinctive factors results in more accurate PGA evaluation. In this study, the two mentioned approaches have been conducted to investigate the seismicity of two vulnerable regions in Iran. For this purpose, 450 seismic catalogues has been used based on five different faults. Results show that DSHA method not necessarily suggests upper bound of PSHA one. Furthermore, the different attenuation relations used has great impact on results of site’s Probable PGA due to considering a various number of effective factors. On the other hand, PSHA results have shown that, when faults divided into subparts lead to more accurate estimations.