Particulate matter (PM) comprises a mixture of chemical compounds and water particles found in air. They mostly have heterogeneous chemical composition and reach the environment from different sources, in different sizes and shapes (in the form of dust, ash, soot, smoke, mineral particles, silicates). In addition to industrial facilities, mobile sources of pollution (traffic) have a significant impact on the emission of suspended particles. According to size, they are divided into two groups: PM10 and PM2.5. The size of suspended particles is directly related to the negative impact on human health and the environment. Children are particularly sensitive to the effects of air pollution because they breathe faster than adults and thus absorb more pollution. According to a research study conducted by the World Health Organization, every year about 100,000 premature deaths of adults occur in the European Union due to air pollution (emissions from road traffic represent a significant share). There are several methods for measuring the presence of suspended particles, such as gravimetry, oscillating crystal microbalance, laser light scattering and β-radiation absorption. The paper presents an analysis of particulate matter pollution in urban areas of the Republic of Croatia. Data on PM10 and PM2.5 concentrations were taken from measuring stations in Zagreb, Slavonski Brod, Osijek, Rijeka and Dubrovnik. The following parametres were analyzed: daily course of PM2.5 and PM10 concentrations, mean values of daily PM2.5 and PM10 concentrations and average daily PM2.5 and PM10 concentrations, during four seasons for the periods from 2017 to 2019. At most measuring stations, maximum concentrations were recorded during autumn and winter, which can be explained by the intensive use of fossil fuels and traffic. Increases in PM concentrations during the summer months at measuring stations in Rijeka and Dubrovnik may be associated with the intensive arrival of tourists by air during the tourist season.