The European Social Survey (ESS) is an academically driven cross-national survey conducted every two years across Europe, in which France has participated since the first round in 2002. The ESS measures the attitudes, beliefs and behaviour patterns of various populations in more than thirty countries. One of its main goals aims to track stability and changes in the social structure of European societies and to provide analysis elements on how Europe’s social, political and moral fabric is changing. In the ESS, data are collected via face-to-face interviews. In France, the fieldwork of the 7th round led to a survey replication on the pilot of the Elipss panel (Longitudinal Internet Studies for Social Sciences). Elipss is a probability based online panel that is representative of the French population aged 18-75. Panel members are randomly selected by The French National Institute of Statistics and Economic Studies (INSEE) and equipped with a touch-screen tablet and a 3G Internet subscription. Every month they are asked to answer a 30 minutes self-administered questionnaire proposed by researchers and selected by a scientific and technical committee. The Center of Socio-Political Data of Sciences Po coordinates the ESS fieldwork for France and conducts the Elipss panel. Consecutively we developed an expertise on the methodology and the process of each mode. The face-to-face fieldwork was carried out from November 2014 to February 2015. To replicate it on the Elipss panel, we used a slot between December 2014 and January 2015. The administration of the first part of the ESS core questionnaire on the Elipss panel gave an opportunity to wonder how the different strategies for collecting data may impact the response behaviour. Knowing that differences are already emerging in the specificities of these two protocols, the questionnaire needed some adjustments that we must consider in such a comparison. Indeed, for its replication in a self-administered mode on a mobile device we had to adapt the design of some questions, and it could have impacted the answer situation. The difference in the structure of the sample should be taken into account to explain the observed differences. The length of the questionnaire, the format of the answer categories, the presence or absence of an interviewer, the survey experience of Elipss panel members could also account for differences in response behaviour. Focusing on type and design of questions, we will pay special attention to the social desirability effect often pointed out in face-to-face surveys. This paper will highlight the specificities of the two survey designs (face-to-face vs self-administered online questionnaire) in order to discuss the scope of such a comparison. Finally, we will compare the answers according to whether the data is collected by interviewers or self-administered on mobile device.