Objective To compare the predicted and actual maximal heart rate (HRmax) values in the cardiopulmonary exercise test (CPET).Methods We retrospectively investigated 1,060 patients who underwent a CPET between January 2016 and April 2020 at our institution’s cardiopulmonary rehabilitation center. The following patients were included: those aged >20 years, those tested with a treadmill, and those who underwent symptom-limited maximum exercise testing— reaching ≥85% of the predicted HRmax (62% if taking beta-blockers) and highest respiratory exchange ratio ≥1.1. Ultimately, 827 patients were included in this study. Data on diagnosis, history of taking beta-blockers, age, body mass index (BMI), and CPET parameters were collected. Subgroup analysis was performed according to age, betablockers, BMI (low <18.5 kg/m2, normal, and high ≥25 kg/m2), and risk classification.Results There was a significant difference between the actual HRmax and the predicted value (p<0.001). Betablocker administration resulted in a significant difference in the actual HRmax (p<0.001). There were significant differences in the moderate-to-high-risk and low-risk groups and the normal BMI and high BMI groups (p<0.001). There was no significant difference between the elderly and younger groups. We suggest new formulae for HRmax of cardiopulmonary patients: estimated HRmax=183-0.76×age (the beta-blocker group) and etimated HRmax=210-0.91×age (the non-beta-blocker group).Conclusion Age-predicted HRmax was significantly different from the actual HRmax of patients with cardiopulmonary disease, especially in the beta-blocker group. For participants with high BMI and moderate-tosevere risk, the actual HRmax was significantly lower than the predicted HRmax.