Abstract: Objective To measure levels of particulate matter less than 2.5 microm in aerodynamic diameter(PM 2.5) in different public places and workplaces and to provide baseline data for tobacco control legislation in Qingdao city.Methods Totally 80 monitoring points were established in 40 restaurants, hotels, government agencies, hospitals, and schools randomly selected in Qingdao city and indoor and outdoor PM2.5 concentrations at the monitoring points were detected and analyzed from June to September 2012.Results The average indoor PM 2.5 concentration for all the monitoring points was 70.0 μg/m³(9.1 μg/m³-228.0 μg/m³), with the lowest mean concentration of 51.2 μg/m³ for the schools and the highest of 97.3 μg/m³ for the restaurants.The logarithmic values(1.93±0.60 μg/m³ and 1.86±0.51μg/m³) of indoor PM2.5 concentration were significantly higher than those of the outdoor for restaurants and hotels (both P<0.05), while there were no significant differences observed in the values between indoor and outdoor measurements for government agencies, hospitals, and schools(all P<0.05).Conclusion The indoor PM 2.5 concentrations are higher for restaurants and hotels but relatively lower in schools and hospitals in Qingdao city, suggesting probable heavy tobacco smoke pollution in some public places and successful implementation of smoking-free policy in hospitals and schools in the city.