Exposure to air pollutants has been associated with adverse health effects. However, analyses of the effects of season and ambient parameters such as ozone have not been fully conducted. Residential indoor and outdoor air levels of polycyclic aromatic hydrocarbons (PAH), black carbon (measured as absorption coefficient [Abs]), and fine particulate matter <2.5 μm (PM)2.5 were measured over two-weeks in a cohort of 5–6 year old children (n=334) living in New York City’s Northern Manhattan and the Bronx between October 2005 and April 2010. The objectives were to: 1) characterize seasonal changes in indoor and outdoor levels and indoor/outdoor (I/O) ratios of PAH (gas + particulate phase; dichotomized into Σ8PAHsemivolatile (MW 178–206), and Σ8PAHnonvolatile (MW 228–278)), Abs, and PM2.5; and 2) assess the relationship between PAH and ozone. Results showed that heating compared to nonheating season was associated with greater Σ8PAHnonvolatile (p<0.001) and Abs (p<0.05), and lower levels of Σ8PAHsemivolatile (p<0.001). In addition, the heating season was associated with lower I/O ratios of Σ8PAHnonvolatile and higher I/O ratios of Σ8PAHsemivolatile (p<0.001) compared to the nonheating season. In outdoor air, Σ8PAHnonvolatile was correlated negatively with community-wide ozone concentration (p<0.001). Seasonal changes in emission sources, air exchanges, meteorological conditions and photochemical/chemical degradation reactions are discussed in relationship to the observed seasonal trends.