Objective To determine the level of awareness of the hazards of tobacco smoking and secondhand smoke inhalation among adults in China. Methods Household surveys were conducted with a total of 13 354 respondents aged 15 years or over from 100 counties of 28 Chinese provinces using a stratified multi-stage geographically clustered sample design. Results The findings revealed that 81.8% of the population was aware that smoking causes serious diseases, and 27.2% and 38.7% were aware that smoking causes stroke and heart attack, respectively. Only 64.3% of respondents were aware that secondhand smoke can cause serious diseases, and 27.5%, 51.0%, and 52.6% were aware that secondhand smoke causes heart disease in adults, lung disease in children and lung cancer in adults, respectively. Awareness regarding smoking-related hazards across all participants was significantly associated with several factors, including gender, smoking status, urban/rural residency, education level and exposure to tobacco control publicity in the last 30 days. Awareness regarding tobacco-related hazards in smokers was significantly associated with urban/rural residency, education level, exposure to tobacco control publicity in the last 30 days, and physician’s advice. Awareness relating to the hazards of inhaling secondhand smoke was associated with smoking status, urban/rural residency, age, education level, and exposure to tobacco control publicity in the last 30 days. Medical professionals were found to know more about the health hazards of tobacco compared with people in other types of employment. Conclusions Overall awareness of the health hazards of tobacco has improved in the last 15 years in China, but is still relatively poor. Improved means of communicating information and more effective warning labels on cigarette packaging are necessary for increasing public awareness of tobacco hazards, particularly among rural residents and people with less education. Objective To determine the level of awareness of the hazards of tobacco smoking and secondhand smoke inhalation among adults in China. Methods Household surveys were conducted with a total of 13 354 respondents aged 15 years or over from 100 counties of 28 Chinese provinces using a stratified multi Results The findings revealed 81.8% of the population was aware that smoking causes serious diseases, and 27.2% and 38.7% were aware that smoking causes stroke and heart attack, respectively. Only 64.3% of respondents were aware that secondhand smoke can cause serious diseases, and 27.5%, 51.0%, and 52.6% were aware that secondhand smoke causes heart disease in adults, lung disease in children and lung cancer in adults, respectively. Awareness regarding smoking-related hazards across all participants was significantly associated with several factors, including gender, smoking status, urban / rural residency, education level and exposure to tob acco control publicity in the last 30 days. Awareness regarding tobacco-related hazards in smokers was significantly associated with urban / rural residency, education level, exposure to tobacco control publicity in the last 30 days, and physician’s advice. Awareness relating to the hazards of inhaling secondhand smoke was associated with smoking status, urban / rural residency, age, education level, and exposure to tobacco control publicity in the last 30 days. Medical professionals were found to know more about the health hazards of tobacco compared with people in other types of employment. Conclusions Overall awareness of the health hazards of tobacco has improved in the last 15 years in China, but is still relatively poor. Improved means of communicating information and more effective warning labels on cigarette packaging are necessary for increasing public awareness of tobacco hazards , especially among rural residents and people with less education.