||Due to the rapidly increasing number of end-stage renal disease patients and the high costs of their treatment, all the aspects of kidney disease that may significantly affect clinical outcome (quality of life mortality) deserve increasing attention. It has been established and accepted that in addition to clinical/somatic factors, also psycho-social factors, including depression, may have a significant impact on the clinical outcome of chronic diseases. Depression is considered to be one of the most prevalent mental health problems in patients with chronic kidney disease. In spite of this fact, there are only few studies on the prevalence, diagnosis and treatment of depression in this population using accurate, well defined diagnostic criteria and appropriate epidemiologic methods. In the last decades we have experienced a significant improvement in the quality and effectiveness of the therapeutic options for chronic kidney disease, but mortality is still very high in this population. Our review provides an overview of the literature regarding the prevalence and etiology of depression, and calls the attention to the interrelation among depression, quality of life and mortality. The second part of our paper to be published later will survey the specific diagnostic and therapeutic features of depression in chronic kidney disease patients.