The ELIPSS Panel (Étude longitudinale par internet pour les sciences sociales) is a French probability-based web panel which is dedicated to surveys in social sciences. Its target population is the French population aged 18-79. Each panel member receives a touchscreen tablet equipped with a 3G/4G connection in order to participate in the self-administrated questionnaires. The monthly surveys are carried out from a specific application pre-installed on the tablet. From 2012 to 2015, the ELIPSS panel was in its pilot stage and is now on the main panel phase since 2016. The pilot was composed of more than 1000 panel members in 2012, 800 among them were still present in 2016. To complete the pilot sample, an offline recruitment of 2500 new panel members was carried out during the first semester of 2016. The questionnaires are designed by research teams after their survey project has been selected by the ELIPSS scientific and technical board. The surveys can be longitudinal or cross-sectional projects. In addition to these surveys, the ELIPSS team conducts each year one core survey to collect sociodemographic data and one survey on the digital practices and the equipment of the panel members. ELIPSS offers a unique opportunity to assess the panel conditioning. Firstly we can study of the evolution in answering of the panel members of the pilot on various topics such as political attitudes, leisure activities and cultural practices, report of socio-demographic characteristics and digital practices. In particular, we will study political attitudes batteries with randomly ordered items at several waves. We will also focus on the internet usage questions since one of the specific aspects of ELIPSS is to provide panel members with a touchscreen tablet connected to the internet. Exploratory results show that non-users of the internet at the entry in the panel became regular users one year after. Secondly, we will be able to compare the pilot sample attitudes and behaviours, which are experienced respondents, with the newly recruited members of the panel. Several waves of the survey on political attitudes and the core survey of ELIPSS are administered at the same time to the two samples in 2016 as well as in early 2017. This paper will address the issue of panel conditioning based on empirical evidences from longitudinal self-administered surveys conducted during four years.