High air pollution concentrations lead to serious health problems in urbanized and industrialized areas. In Istanbul, Golden Horn is a creek valley which is identified by its special terrain that makes air pollutants difficult to disperse. The goal of this study is to determine the ozone levels in this region, considering that reducing of ozone precursor emissions accomplishes surface ozone control. Ozone in surface boundary layer is formed by photochemical reactions involving nitrogen oxides, and is affected by urbanization, traffic and industry. In order to investigate the air quality levels in Golden Horn, the surface ozone concentrations and its precursors (NO and NO2) in Alibeykoy and Kagithane regions are temporally analyzed herein. Moreover, the relationship of ozone with precipitation is also determined.