Purpose The purpose was to investigate what effect an intervention of low-dose, high-frequency cardiopulmonary resuscitation (CPR) training with feedback for one month would have on professionals' subjective self-assessment skill of CPR. Design/methodology/approach This study had a quantitative approach. In total, 38 firefighters performed CPR for two minutes on a Resusci Anne QCPR. They then self-assessed their CPR through four multiple-choice questions regarding compression rate, depth, recoil and ventilation volume. After one month of low-dose, high-frequency training with visual feedback, the firefighters once more performed CPR and self-assessed their CPR. Findings With one month of low-dose, high-frequency training with visual feedback, the level of self-assessment was 87% (n = 33) correct self-assessment of compression rate, 95% (n = 36) correct self-assessment of compression depth, 68% (n = 26) correct self-assessment of recoil and 87% (n = 33) correct self-assessment of ventilations volume. The result shows a reduced number of firefighters who overestimate their ability to perform CPR. Originality/value With low-dose, high-frequency CPR training with visual feedback for a month, the firefighters develop a good ability to self-assess their CPR to be performed within the guidelines. By improving their ability to self-assess their CPR quality, firefighters can self-regulate their compression and ventilation quality.