The survey of 1929 adults in Switzerland in the period from 17 - 26 April 2020 suggests that a large majority of the population in any case or probably intends to a) install an app for contact-tracing of SARS-CoV-2, b) report infections in the app and c) comply with the app's request for contact reduction or domestic quarantine. The survey was based on the scenario of an «anonymous» app for voluntary contact-tracing via Bluetooth (e.g. DP-3T), which does not collect location and movement data, but can only register other app users in the vicinity. The main reasons for using the app are a sense of responsibility towards the general public (73% of respondents), the protection of one's own family and friends (67%) and a contribution to reducing deaths among older people and people with pre-existing conditions (50%). The respondents also cite reasons that would speak against using an app for them. 40% are concerned that the state could use the app as an excuse for increased surveillance during or after the pandemic. 39% express the concern that the app does not work (e.g. false alarms). The composition of the respondents corresponds to the structure of the adult Swiss population by age, gender and major regions.