Introduction: Out-of-hospital cardiac arrests (OHCA) of presumed cardiac origin witnessed by nonfamily members in the daytime are most effectively resuscitated in the youth, in which the impact of recently disseminated hands-only cardiopulmonary resuscitation (CPR) is poorly understood. Hypothesis: Dissemination of hands-only CPR is associated with the better outcome in school students and young adults after such OHCA. Methods: We investigated OHCA of presumed cardiac origin in the youth (Group A, 7-12y; group B, 13-18y; group C, 19-22y; group D, 23-35y) which are witnessed by nonfamily members in the daytime (6:00-17:59) during 2005-15 by using Japanese nationwide Utstein registry. Results: We recruited 1,646 pts, in which N of pts was 92 (A), 382 (B), 229 (C) and 943 (D); ventricular fibrillation (VF) as the initial rhythm (%) was 48, 70, 64, and 59; bystander’s CPR (%) was 81, 80, 71 and 68; hands-only/bystander’s CPR (%) was 32, 38, 57, 56; bystander’s automated external defibrillator (AED) (%) was 37, 44, 24 and 19; the favorable neurological outcome at 1 month (CPC1-2)(%) was 46, 49, 39 and 30. Compared with group D, %bystander’s CPR (p=.013 in A, <.001 in B), %bystander’s AED (<.001 in both), and %CPC1-2 (.005, <.001) was higher but %hands-only CPR(<.001 in both) was lower in A and B, independent of the calendar year. Compared with 2005-09, %hands-only CPR, %bystander’s AED and CPC1-2 were higher in all age groups (<.005 in all) in 2010-15. In multivariate logistic analysis (gender, age groups (vs D), CPR type (conventional or hands-only CPR vs no CPR), bystander’s AED, the initial VF, emergency response time, calendar year), hands-only CPR (p=.03), bystander’s AED(<.001), female gender(.045), initial VF (<.001), emergency response time (<.001), and calendar year (<.001) were independently associated with CPC1-2. Conclusions: The present investigation demonstrates that resuscitation and outcome parameters after OHCA of presumed cardiac origin were persistently better in school students than young adults and that %hands-only CPR, which was persistently lower in school students, was independently associated with the better outcome in the youth overall. This finding may give a clue to further improvement of the outcomes in school students after OHCA.