On-site odor measurements and mathematical modeling are useful for identifying the odor impact at the source and receptors located in areas adjacent to wastewater treatment plants (WWTPs). Impact of open area sources can be significant and may influence air quality both at the WWTP area and downwind in the surrounding areas. In this work, results of the odor measurements carried out in the spring and summer season for sources within three different mechanical-biological WWTPs in Poland are presented. The odor impact assessment was completed using a Polish reference model. The odor emission scenarios considering the contribution of major odor sources within WWTPs and the seasonal variation were determined. Obtained results showed significant differences between spring and summer seasons. The highest and the lowest measured odor concentrations at the WWTP property line were 75 ouE/m3 (July) and 6.4 ouE/m3 (March), respectively.