There is some evidence that breaking a survey into several pages may increase breakoffs inmobile web surveys compared to a scrolling design where all items are presented on the same page. However, to our knowledge, there is almost no empirical evidence on the optimal number of items or questions to include on a page in a mobile web survey. We investigate the effect of the number of items presented on the screen on data quality in two types of questionnaires – with or without user-controlled skips. Three scrolling options were compared in a survey with 30 items where 5, 15, or all 30 questions were presented on a page. We conducted a randomized experiment using a volunteer online access panel in Russia. Panelists were invited to complete the survey via mobile phone, with random assignment to one of the six conditions. A total of 2,032 respondents completed the survey with an overall completion rate of 26.3%. We found that displaying all 30 items on a page reduced the breakoff rate by almost a third compared to presenting 5 items per page in the questionnaire without skips. In both surveys with and without skips the completion time was significantly lower in the 30-items per page condition; however, it also resulted in higher overall item nonresponse rate. No effect was found for the number of the items displayed on the screen on measurement error in both closed-and open-ended questions. Though the questionnaire with skips did not produce a higher breakoff rate than the questionnaire with skips, there is evidence of motivated underreporting when participants could skip two open-ended questions in a row. We will present our research findings and offer some practical recommendations for questionnaire design for mobile web surveys, depending on the research goals.