The purpose of this cross-national study was to determine the leading social influences on smoking among Chinese Americans and mainland Chinese adults with the aim of improving prevention and intervention strategies to reduce smoking rates. A comparative cross-sectional design was used and a stratified-cluster sampling technique was employed in identifying the study sample. An 80-item questionnaire was administered in Chinese to 1222 participants, 812 in China and 410 in the U.S. Data were analyzed using descriptive and inferential statistical tests. Results contain comparative data on social influences of smoking among Chinese Americans and mainland Chinese, as well as factors influencing smoking behavior which include cultural beliefs, gender roles, and family relationship dynamics. Grandparents were influential and significantly correlated with current smokers in China. Findings indicate differential effects of social influences on smoking behavior. Similarities and differences provide a basis for improving and/or developing smoking intervention programs of mutual benefit to China and the U.S..