Aim <p>This study aimed to compare comorbidities’ prevalence and the comorbidity burden as measured by comorbidity indices according to the stages and the etiological diagnoses of neurocognitive disorders (NCD). This study aimed also to examine how comorbidities and comorbidity indices were associated with both stages and etiologies of NCD.</p> Methods <p>This is a cross-sectional study including participants from the MEMORA real-life cohort, aged ≥ 60&#xa0;years. Patients had to be in either MCI or dementia stage, with the following etiological diagnoses of NCD: AD, VD (vascular dementia), mixed dementia (MD), dementia with Lewy bodies, frontotemporal dementia and Parkinson’s disease. Three comorbidity indices were used to measure comorbidity burden: the Charlson comorbidity index, the multimorbidity-weighted index (MWI) and the health-related quality of life comorbidity index (HRQOL-CI). Prevalence of comorbidities involved in the calculation of at least one comorbidity index were reported. The associations between comorbidities/comorbidity indices and groups were assessed using binary and multinomial logistic regressions.</p> Results <p>Overall, 3470 patients (66.9% dementia; 50.9% AD) were included. The most frequent comorbidities were hypertension (50.2%), depression (28.0%) and hypercholesterolemia (22.6%). The MWI and the HRQOL-CI were associated with increased odds of dementia (vs. MCI). Upon stratifying population according to the etiological diagnoses of NCD, the highest mean of the three comorbidity indices were found in patients with VD and MD.</p> Conclusion <p>Comorbidities and comorbidity burden vary according to the stage and etiological diagnoses of NCD. Future studies should consider the stage and the etiological diagnoses, when studying the effect of the comorbidity burden on the progression of NCD.</p>