This article investigates item nonresponse in open-ended survey questions because such item nonresponse is much higher than in closed questions. The difference is a result of the higher cognitive burden placed on the respondent. To study item nonresponse, we manipulate different questionnaire design characteristics, such as the size of the answer box and the inclusion of motivation texts, as well as respondent-specific characteristics, in a randomized web experiment using a student sample. The results show that a motivation text increases the frequency of responses to open-ended questions for both small and large answer boxes. However, large answer boxes earn higher item nonresponse than small answer boxes regardless of the usage of a motivation text. In addition, gender and the respondent's field of study affected the answering of open-ended questions; being a woman or studying social sciences increased the frequency of a response. As the major finding and in contrast to previous findings, our results indicate that particularly large answer boxes should be avoided, because they reduce respondents' willingness to respond.