Particulate matter consist of a complex, heterogeneous mixture of solid and liquid components whose composition changes in time and space, and depends on emission from various sources and weather conditions. According to size, they are divided into coarse particles whose aerodynamic diameter is less than 10 μm (PM10) and fine particles with a diameter less than 2.5 μm (PM2.5). Emitted particles have a negative impact on human health and the quality of the environment. One of the main sources of suspended particles is traffic. Emissions from road traffic can be divided into primary and secondary particles from combustion engines, and into primary and secondary particles from brake, tyre and road wear Plitvice Lakes is the largest and oldest Croatian National Park, which with its exceptional natural beauty attracts many visitors from all over the world. Due to the constant increase in the number of visitors (a double increase in the last 10 years), and the transit traffic on state roads that is not related to visiting the park, there is traffic pressure in the immediate vicinity of the lakes and entrance receptions. The aim of the study was to examine the relationship between daily traffic and daily concentration of particulate matter (PM2.5) in the Plitvice Lakes National Park in 2018 and 2019. It was found that the seasonal increase in the amount of traffic does not lead to an increase in the concentration of fine particulate matter, ie that there is no correlation between these variables. Although traffic has not significantly contributed to particulate matter pollution, it can degrade the environment with noise and vibration, jeopardize the stability of travertine barriers, endanger wildlife, and cause lake and groundwater pollution. Therefore, relocating transit traffic outside the Park area is of utmost importance for the protection of this global phenomenon.