Apart from meteorological factors affecting air pollution levels in big cities as Tehran (which have a rather low mean annual wind speed for ventilation), the level of vehicular emission reduction due to the reduction of the traffic is also important. The aim of this research is to find out the effects of weekend reduced emission on reduction of air pollution in Tehran. To avoid the effects of active synoptic systems on air pollution, the warm period of the year for which they are minimal, are chosen. Comparison of the levels of particulate and gaseous pollutants show that the effect of weekend is negligible on air pollutant reduction, except for the NOx form which the maximum reduction is for NO. It appears that the reduction of emissions from natural gas consuming vehicles and cars could be the main reason for the reductions of NOx at the weekends. The levels of early morning weekend traffic reductions of NO and NO2 are respectively 59 and 30 percent, as compared to that of days before and after weekday levels. Also, the highest weekend reductions occur in central areas of Tehran, e.g. Sharif University and Tarbiat Modaress University stations and to some extent in Shadabad station, south west of Tehran. While for the monitoring stations around the city, as Aghdasieh, Ponak, Ray city, they experience least reduction in air pollution at the weekends. Region 19 and around the Mehalati freeway have almost no reduction in air pollutants.