Air pollution is one of the major problems ofmegacities in the world. Particulatematter, which is the primary component of air pollution, has several adverse effects on environment and humankind. In megacities, many children spend their free time in playgrounds; consequently most of the air pollutants like particulate matter affect urban children. Although particulate matter concentrations may give an idea on the level of air pollution, particle number concentration in ambient air is an important parameter for understanding the short-term effects on the human respiratory system. However, available data on particle number concentrations in various size ranges are not sufficient to clear the issue. In this study, we measured the particle number concentration in the selected playgrounds of a megacity, Istanbul, using a light scattering particle counter. Particle number distributions were determined on 90 days during the spring 2009. Results showed that particles smaller than 2.5 mm were high in number concentrations in the playgrounds, which were close to the major roads, where the traffic was much more dense. Consequently, a few suggestions were made regarding the location of playgrounds in urban areas. © 2010 DEStech Publications, Inc.