Purpose: We identified an age range in which comorbidity is most closely associated with premature mortality after radical prostatectomy. Materials and Methods: A total of 1,302 patients selected for radical prostatectomy were stratified according to the Charlson score, the American Society of Anesthesiologists physical status classification, the New York Heart Association classification of heart insufficiency and the classification of angina pectoris of the Canadian Cardiovascular Society. Furthermore, patients were subdivided into several age groups. Comorbid mortality and overall mortality were the study end points. The prognostic relevance of the comorbidity classifications was assessed by comparing Mantel-Haenszel HRs, p values and 10-year overall survival rates. Results: The discriminative capacity of all 4 investigated comorbidity classifications decreased when patients 70.0 years or older were included with decreasing HRs and increasing p values. Except for the American Society of Anesthesiologists classification HRs for comparing the high vs low risk groups tended to decrease and p values simultaneously tended to increase when patients younger than 63.0 years were included. In the age range of between 63.0 and 69.9 years 10-year overall survival rates differed by 14% to 28% between patients with a high vs low comorbid risk compared with 6% to 13% in the whole sample. Conclusions: The discriminative capacity of the investigated comorbidity classifications was greatest in the age group that was 63.0 to 69.9 years old. In patients younger than 63.0 or older than 70.0 years comorbidity classification seemed to contribute little to the prediction of comorbid mortality.