With increasing age of a population, the rate and severity of comorbidities are also growing, resulting in a rising number of people with a condition described as "cardiorenal syndrome". Initially, cardiorenal syndrome defined the decline in cardiac and renal function due to diminished renal perfusion in the context of heart failure. However, in order to give consideration to the numerous comorbidities, nowadays the definition has been widened. Following a new classification, five types of cardiorenal syndrome are distinguished. Such a differentiation is helpful to find the appropriate therapeutic approach, according to the underlying disease. Therefore, the new classification and modern therapeutic concepts shall be presented here.