Objectives: This study purports to comparatively study health condition, health behaviors, and health care utilization of Koreans living in Korea and in the US, and then, to analyze the factors influencing them. Methods: The collected data were analyzed on the basis of the 2005 Korea National Health and Nutrition Examination Survey. Of 25,196 adults aged 19 or older, 7,802 respondents to health behavior survey and 5,526 respondents to physical examination survey. The analyzed data of the Korean Americans were the results of the California Health Interview Survey (CHIS) conducted by the UCLA Center for Health Policy Research in 2005. This study analyzed the responses of 645 known Korean respondents to the 2005 CHIS. Results: In regard to differences in overall health condition between the two groups, it was found that both the male and female Korean Americans thought their own overall health conditions were relatively poor compared to Koreans, especially in relation to diabetes and cardiovascular diseases. For smoking status considered as one of health behavior factors, smokers of the Koreans account for 46.1% which is higher than that of the Korean Americans and the proportion of the Koreans smoking daily is also at least two times higher than that of the Korean Americans. Similarly, for alcohol drinking, the Koreans showed higher drinking experience rate and no less than three times higher drinking frequency than that of Korean Americans. Conclusion: It is expected that this study will contribute greatly to solving health problems among foreign immigrants and overseas Koreans in future by clarifying any differences in health status and health behaviors resulting from sociocultural differences despite of similar genetic factors.