Abstract In the work is presented the investigation of seismicity of the region where the Kozloduy NPP site is located. This paper intends to present an overview of issues concerning earthquake assessments and relevant activities at the Bulgarian nuclear power plant site – Kozloduy NPP. The overview, based on all the available literature sources, includes: the seismicity of the region where the NPP site is located, the seismic design bases – reassessment and current situation, and seismic hazard assessment for the Kozloduy NPP site as well as the experience of INRNE experts on these topics. Furthermore, this paper describes the basic requirements related to the seismic hazard assessment, specified by the IAEA guidances and the Bulgarian regulations, presently in force. The presented work can be used in further work concerning extending of safety assessment of NPP against the availability of such external events as earthquakes for demonstration of safety operation of NPP.