Mixed-mode surveys can be used when survey practitioners face time or budget constraints as well as for other research purposes. Previous research has shown the mode of survey interview can sometimes affect the way in which questions are answered, especially for sensitive questions. Using data from a pair of recent Pew research center surveys of veterans in the U.S., we explore the possible mode effects on the data quality of post- 9/11 veterans samples in this study. To oversample the post-9/11 veterans in the survey, we used both phone (n=498) and internet interviews (n=214 from the Knowledge Networks panel). We analyzed whether there were differences between the two samples to ensure that the data from the two modes were comparable. The preliminary results suggest that the differences in responses between the two modes were modest in size and most were not statistically significant. Statistically significant differences were found in 19 of the 60 substantive questions in the survey, although the pattern was not consistent. The sample of post-9/11 veterans who responded by phone and those who responded online were somewhat different on a few characteristics. There were no significant differences by gender, age, race or ethnicity, but more phone than web respondents had never attended college and fewer were currently married. Results from Logistic regression models show that after controlling for all demographic variables , a significant effect by mode of interview was found for 6 of the 19 questions, including whether it is best for the U.S. to be active in world affairs, satisfaction with their personal finances and how good the care for injured veterans is at U.S. military hospitals.