Kidney transplantation (KT) is the treatment of choice for end-stage renal failure, but such patients are increasingly older and have additional comorbid conditions leading to high mortality rates after transplantation. Delayed graft function is a common complication after KT, especially in recipients who receive expanded criteria donor, and these complications are associated with a poorer graft survival in the long term. Taken together, an appropriate assessment of comorbidity grouped in prognostic indexes could be a useful tool to make crucial therapeutic decisions at the time of transplant. Allocation systems based upon a recipient risk score, as well as identification of risk factors for delayed graft function, may improve outcomes after KT. The aim of this review is to assess the contribution and utility of comorbid conditions, grouped in prognostic indexes to predict and improve kidney transplant outcomes.