Background: Little is known regarding circumstances, outcomes and quality of cardiopulmonary resuscitation (CPR) and the use of automated external defibrillators (AEDs) performed by operational lifeboat crews. Our aim is to evaluate circumstances, outcomes and quality of CPR performed by the Royal Dutch Lifeboat Institution (KNRM) in out-of-hospital cardiac arrest (OHCA)., Methods: The internal KNRM database has been used to identify and analyse all OHCA cases between July 2011 and December 2017. A limited set of AED data was available to study the quality of CPR., Results: In 37 patients the lifeboat crew members have performed CPR, of which 29 (78.4%) occurred under hostile conditions. The median response time to arrive at the location was 15min. In 11 (29.7%) patients return of spontaneous circulation was achieved at any moment during CPR and 3 (8.1%) patients were still alive after one month. The lifeboat AED was used in 12 patients. Their recordings show a high median compression frequency (120, IQR 111-131) and prolonged median interruption periods (pre-analysis pause 11s (IQR 10-13), post-analysis pause 4s (IQR 3-8), pre-shock pause 24s (IQR 19-26), post-shock pause 6s (IQR 6-11), ventilation pause 6s (IQR 4-8) and other pauses 9s (IQR 4-17))., Conclusions: Compared to most out-of-hospital resuscitations, resuscitations by lifeboat crews have a low incidence, occur under difficult circumstances and in a younger population. AED's on lifeboats have not contributed to any of the survivals. Analysis of AED information can be used to study the quality of CPR and provide input for improving future training of lifeboat crews., (Copyright © 2019 Elsevier B.V. All rights reserved.)