Abstract Background Out of hospital cardiac arrest remains a big issue worldwide, with more than 700.000 deaths annually. Many lives could have been saved if more people had been trained in cardiopulmonary resuscitation. The World Health Organization endorsed the “Kids Save Lives” project in 2015 in order to reduce mortality, while countries, where children were taught cardiopulmonary resuscitation (CPR) in schools, have higher rates of bystander CPR and higher survival rates. Purpose To evaluate the level of theoretical knowledge, willingness to perform Cardiopulmonary resuscitation (CPR) and active skills of Greek secondary school students on the subject of Basic life Support before and after a “Kids Save Lives” program. Moreover to evaluate the potential benefits of training for 3 consecutive years Material and method Data collection took place on the academic periods of 2017–2018, 2018–2019 and 2019–2020 and was performed in secondary schools of Thessaly's region. A total of 5823 students (51,9% female, mean age 14.2 years) participated on the “Kids save Lives” program according to the European Resuscitation Council (ERC) and World Health Organization (WHO) statement. The program was under the approval of Greek Ministry of Education. 709 students followed the program for two consecutive years and 202 for three consecutive years. A 12-question questionnaire was answered by the students before and after the “kid saves lives” program, while practical skills were evaluated on manikins by experienced Basic Life Support Instructors. Results The training improves significantly the theoretical knowledge regarding CPR, with the percentage of correct answers being 48,65%, 63,88%, 75,70% before the first, second and third years respectively (p<0.001). After the course the percentages of correct answers went up to 83,26%, 87,95% and 92,67% after the first, second and third years of the course respectively (p<0.001). The participants willingness to perform bystander CPR significantly increased after the completion of the first year of course (93,8% before to 97,4% after, p<0.001) and remains highly for the next 2 years. Almost all of the participants (98.9%) could recognize the correct position near the victim and 91% performed chin lift maneuver and recognized cardiac arrest. More than 90% of the students performed chest compressions with the correct rate and placing their hands on the center of the chest (90,1% and 93.4%, respectively), whereas only 76.4% of the participants achieved the desired compression depth of 5 to 6 cm. One year later there was improvement to their skills and especially to the desired depth of chest compression (87,6%, p<0,001) Conclusions The overall results strongly depict the benefits of “Kids Save Lives” program by improving the theoretical knowledge, the practical skills and the attitude of Greek students towards CPR and indicate the need for its implementation for 3 consecutive years for every student. Funding Acknowledgement Type of funding sources: None.