Dropouts can be a significant problem in web surveys, but theoretically motivated studies of this problem are rare. In this study, we use a dynamic theory of decision making, the decision field theory, to predict and explain behavior of respondents in a web survey. By registering respondents’ momentary subjective experiences throughout the survey, we gained some insights into antecedents and consequences of respondents’ decision to drop out. The results show that interest and experienced burden change throughout the survey, depending on characteristics of questions, respondents, and survey design. Respondents who drop out often express lower interest and higher experienced burden than the respondents who stay. Their growing preference for dropout can be detected in the decreased quality of their answers even before the point of dropout. The results could help in practical work and open new paths to theoretical explanations of survey behavior.