Onco-nephrology is a new field of medicine which combines many aspects of kidney injury in cancer patients and cancers in patients with kidney disease. This connection takes many forms and includes drug-induced nephrotoxicity, electrolyte disorders, numerous paraneoplastic syndromes and an increased rate cancers in dialysis and transplanted patients. The appropriate laboratory assessment of the kidney function allows to optimize chemotherapy and thus minimizes the risk of complications. This article focuses on acute kidney injury (AKI), chronic kidney disease (CKD), various electrolyte and acid-base disorders, the most common cancers after kidney transplantation and the kidney disorders associated with HSCT (hematopoietic stem cell transplantation). The possibility of the application of novel cancer therapy, such as cancer immunotherapy and proton therapy in transplant recipients was also discussed.