Introduction: Smartphone technology is increasingly used to engage lay people as volunteer responders in resuscitation attempts. Attention has recently been drawn to how resuscitation attempts may impact bystanders. Attempting resuscitation in out-of-hospital cardiac arrests (OHCA) may be an overwhelming experience and, in some cases, difficult to cope with. We developed a volunteer responder follow-up program to systematically measure the psychological and physical impact on volunteer responders dispatched for OHCAs. Methods and Results: The nationwide Danish volunteer responder program dispatches volunteer responders for presumed cardiac arrests. 90 min after notification of a potential nearby cardiac arrest, all volunteer responders receive a survey, and are asked to self-report their mental state of mind after the event. The volunteer responders are also asked to disclose any physical injury they sustained in relation to the event. Volunteer responders who report severe mental effects are offered a defusing conversation by a trained nurse. Between 1 September 2017 and 31 December 2022, the Danish volunteer responder program has alerted 177,866 volunteer responders for 10,819 presumed cardiac arrest alerts. Of 177,866 alerted volunteers responders, 62,711 accepted the alarm. In the same period, 7,317 cancelled their registration. From January 2019 to 31 December 31 2022, a total of 535 volunteer responders were offered a defusing consultation. Conclusion: The Danish volunteer responder follow-up program is carried out to assess the psychological and physical risks of responding to a suspected OHCA. We suggest a survey-based method for systematic screening of volunteer responders that allow volunteer responders to report any physical injury or need of psychological follow-up. The person providing defusing should be a trained and experienced healthcare professional.