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Introduction The chronic obstructive pulmonary disease (COPD)-specific comorbidity test (COTE) aims to predict long-term mortality in patients with COPD, whereas the Charlson comorbidity index (CCI) score is used as a validated tool for predicting long-term mortality across medical conditions. Comparison of the two comorbidity scores’ ability to predict mortality has only been studied scarcely.Aims and objectives This study aimed to compare the predictive ability of the COTE and CCI scores including the updated CCI score with updated weights (CCI (Quan)) in patients with COPD following acute exacerbation of chronic obstructive pulmonary disease (AECOPD).Methods Using nationwide registry data, all Danish patients at first admission due to AECOPD during 2005–2018 were included in this retrospective cohort study. 1-year mortality was explored including age, sex and CCI or COTE comorbidity scores. Logistic regression was performed with fivefold cross-validation comparing area under the curve (AUC) and optimal threshold using Youden index. The logistic regression models were furthermore examined using 10 000 bootstrap analyses and comparing the distribution of accuracy using a T-test. Cox regression analysis was used to compare Brier scores over time for models including combinations of age, sex, COTE, CCI and CCI (Quan).Results A total of 87 271 individuals were identified with a first-time AECOPD during the study period. The median age was 74 IQR (66, 81) and 48.4% were males.The logistic regression revealed an AUC of the CCI and CCI (Quan) models of 0.714 and for the COTE model 0.707 (p<0.001).Comparison using T-test on 10 000 bootstrap samples revealed small differences with an accuracy of 0.7281 (95% CI 0.7241 to 0.7320) for the COTE model and 0.7275 (95% CI 0.7235 to 7314) for the CCI model (p<0.001).Brier scores were 0.1793 for CCI, 0.1789 for CCI (Quan) and 0.1802 for COTE, only slightly favouring the CCI model.Conclusions In a cohort of patients with first-time AECOPD, we found similar predictive abilities of 1-year mortality comparing the CCI, CCI (Quan) and COTE score.