This study consists of three sub-studies. Sub-study 1 and 2 attempted to incorporate environmental variables as precursor background variables of the theory of planned behavior (TPB) to predict quitting-related intentions among Texas adult smokers and university student smokers, respectively. Sub-study 1 and 2 analyzed different data sets and were conducted using the same methodology for the comparison. A total of 395 Texas adult smokers and 379 university student smokers were analyzed using multiple structural equation modeling. The extent of agreement with regulating smoking in public places had positive indirect effects on intention to take measures to quit through attitude (ß = 0.02, p < 0.01) and subjective norm (ß = 0.03, p < 0.01) among Texas adult smokers. The extent of agreement with regulating smoking in public places had significant positive indirect effect on intention to quit through subjective norm (ß = 0.01, p < 0.05) among university student smokers. The number of smokers among 5 closest friends had negative indirect effect on intention to take measures to quit through subjective norm (ß = -0.02, p < 0.05) among Texas adult smokers. The results of this study may contribute to the literature by providing valuable information suggesting that environmental variables need to be considered as precursor background variables of the TPB to predict quitting-related intentions. Sub-study 3 investigated differences in the relationship between cigarette smoking and other key health behaviors, such as vigorous physical activity, fruit and vegetable consumption, and binge drinking among young adults (ages 18 to 30 years) across 180 metropolitan and micropolitan statistical areas (MMSAs) in the United States. A total of 19,027 young adults in the 2009 Behavioral Risk Factor Surveillance System (BRFSS) data were analyzed using multilevel logistic regression models. There were significant differences in the relation of smoking with vigorous physical activity, fruit and vegetable consumption, and binge drinking across the 180 MMSAs. These differences were associated with the prevalence of cigarette smoking and binge drinking for each MMSA. The results of this study suggest that it is important to take into account geographic area-specific prevalence of key health behaviors in needs assessment to plan community health promotion programs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]