Electrospun nanofibrous filter media have attracted considerable attention in the last decade. The present study aimed to develop the electrospun PAN (polyacrylonitrile) filter media through experimental investigations for application in high-performance air filters. For this purpose, an experimental design was proposed to assess the effect of electrospinning process conditions including solution concentration, electric voltage and nozzle-collector distance on the structural properties of filter media including the fiber diameter, percent of porosity and bead number. Optimization of electrospinning parameters was conducted through the Response Surface Methodology to obtain the desired values for fibrous media variables. The morphology of the mats (including bead number and fiber diameter) were studied using SEM images through, Microstructure Measurement image analyzer. The porosity was determined using image analysis algorithms by MATLAB. The findings indicated that the concentration is the most influencing factor on fiber diameter (r= 0.73, p<0.05) and bead number (r= -0.51, p>0.05), so that the lower concentrations led to lower fiber diameter and more bead number. Among the electrospinning parameters, the highest correlation coefficient was achieved between porosity of PAN media and applied voltage (r=0.39, p>0.05). There was a negative relationship between fiber diameter and both percent of porosity (r=-23; p>0.05) and bead number(r=-0.53; p<0.05). Thus, media with the lower fiber diameter had the higher porosity and more bead number. Since the fibers diameter, bead number and porosity can have different effects on the quality factor of filters, the well-considered selection of electrospinning conditions can be of great importance for obtaining the arbitrary values of filter characteristics.