Lithium salts are the recommended first-line treatment (gold standard) in national and international treatment guidelines for acute and maintenance treatment of affective disorders, such as bipolar disorders. Lithium has also been shown to have a unique protective effect against suicide in patients suffering from affective disorders. Despite the well-known acute and long-term adverse effects lithium therapy can be safely administered if patients are properly educated and carefully monitored. A recent study from France now shows that patients with severely impaired renal function who had been treated with lithium salts for more than 10 years could have an increased risk for kidney tumors (benign and malignant). This resulted in an adjustment concerning information within the package leaflet by European authorities. The authors of this article reflect the currently available data in order to better understand and handle this new finding and to warn about uncritical reactions including withdrawal of lithium in successfully treated patients. This article provides clinical recommendations to provide further insight relating to the risk of kidney cancer in long-term lithium therapy.