Increasingly, survey data is being collected by more than one mode. Some surveys use a combination of web (CAWI) and telephone (CATI) collection; others may use a combination of telephone and face-to-face interviewing. For many types of questions, the distribution of response options may be different in the two (or more) mode samples. The difference is partly attributable to selection effects, for example, due to web and telephone respondents being recruited in different ways, or using different frames. Typically, web and telephone samples differ with respect to their distributions of age, sex, education and variables related to personal outlook. Another source of difference in the response option distribution is "technical" in origin, having to do with respondents’ tendency to process the options differently depending on whether the options are heard or seen. Thus, for example, it is often found that telephone respondents are more likely than web respondents to use the extremes of a Likert scale. The purpose of this presentation is to illustrate an approach to modeling in a mixed mode survey that takes into account both selection and technical mode effects, using data from the International Tobacco Control (ITC) surveys in the Netherlands and Malaysia. The model uses a propensity score for selection effects, and up to two parameters for technical effects. It can be extended to apply to cross-country comparison data, or to longitudinal data where the collection mode may change from wave to wave.