Abstract: This report analyses an experiment conducted in waves 2, 4 and 6 of the CROss-National Online Survey (CRONOS) panelin the three participating countries, Estonia, Slovenia and Great Britain. The second wave was conducted between April and June 2017. The fourth and the sixth wave were open, respectively, from September to October 2017, and January to February 2018.This experiment is intended to establish the impact of motivational messages in web surveyson data quality.Respondents were randomly assigned into a control group and two treatment groups in Wave 2 and were kept in the same group for the remaining two waves. Four to five other messages (depending on wave) were placed throughout the questionnaire.The control group respondents were only displayed a neutral introduction, while those in the treatment groups were also presented additional motivational text, emphasizing the positive or the negative consequences of their behaviours. In order to establish the impact on data quality, we compare control and treatment groups in terms of break-offs, item nonresponse, non-differentiation, completion time, efforts reported and evaluation of the survey experience.