Purpose: To assess the knowledge of laypersons before and after courses in Basic Life Support (BLS) and use of Automated External Defibrillators (AED). Methods: We trained 158 candidates (93 women, age 39 ± 13 years old) in free BLS/AED courses accredited by the European Resuscitation Council (ERC). Trainees were relatives of patients with coronary artery disease and completed 15-point questionnaires before and after the course. Courses were offered free of charge. Candidate responses were analysed with the McNemar and Wilcoxon tests. Results: All trainees passed the course. Of the 158 candidates, 71 (45%) were the patient's offspring and 44 (28%) the spouse, 104 (66%) had a University education, 116 (73%) spoke English, 105 (66%) had heard about resuscitation before and 13 (10%) had attempted to resuscitate a cardiac arrest victim, but only 15 (9%) had any previous training. Before the course, only 15% of trainees considered their knowledge to be adequate, compared to 98% after (p < 0.0001). Before, 23% estimated that survival from out-of-hospital cardiac arrest was 5–10% but 44% after (p = 0.01). Only 47% knew the emergency dialing number (112) in the EU before the course but 87% after (p < 0.0001). Before, 31% of trainees were willing to resuscitate a relative and 21% willing to resuscitate a stranger, compared to 92% and 74%, respectively, after (p < 0.0001 for both). Before, 41% knew that Athens International Airport is equipped with AEDs but only 8% were willing to operate them, compared to 99% and 96%, respectively, after (p < 0.0001 for both). All candidates supported the training of laypersons in resuscitation, 93% agreed that Greek legislation must change to allow non-doctors to defibrillate, and 77% were willing to buy an AED at home. Conclusions: Relatives of patients at risk for cardiac arrest who are trained in BLS/AED courses improve their knowledge of resuscitation, willingness to resuscitate a relative or a stranger, and confidence in using an AED.