INTRODUCTION: In our national emergency dispatch centre, the standard protocol for dispatcher-assisted cardiopulmonary resuscitation (DACPR) in out-of-hospital cardiac arrests (OHCAs) involves the instruction 'push 100 times a minute 5 cm deep'. As part of quality improvement, the instruction was simplified to 'push hard and fast'. METHODS: We analysed all dispatcher-diagnosed OHCAs over four months in 2018: January to February ('push 100 times a minute 5 cm deep') and August to September ('push hard and fast'). We also performed secondary per-protocol analysis based on the protocol used: (a) standard (n = 48); (b) simplified (n = 227); and (c) own words (n = 231). RESULTS: A total of 506 cases were included: 282 in the 'before' group and 224 in the 'after' group. Adherence to the protocol was 15.2% in the 'before' phase and 72.8% in the 'after' phase (p < 0.001). The mean time between instruction and first compression for the 'before' and 'after' groups was 34.36 seconds and 26.83 seconds, respectively (p < 0.001). Time to first compression was 238.62 seconds and 218.83 seconds in the 'before' and 'after' groups, respectively (p = 0.016). In the per-protocol analysis, the interval between instruction and compression was 37.19 seconds, 28.31 seconds and 32.40 seconds in the standard protocol, simplified protocol and 'own words' groups, respectively (p = 0.005). The need for paraphrasing was 60.4% in the standard protocol group and 81.5% in the simplified group (p < 0.001). CONCLUSION Simplified instructions were associated with a shorter interval between instruction and first compression. Efforts should be directed at simplifying DACPR instructions.