Personalized diagnosis and treatment are particularly important in cases of erotomania, a rare mental illness that poses a huge challenge to the psychiatric care system. This paper reviews contemporary knowledge about erotomania (de Clérambault syndrome). It discusses the scope of the concept, terminology used, historical data, epidemiology and etiopathogenesis, nosological position, symptoms and clinical course, treatment and prognosis. Diagnostic and therapeutic difficulties in patients with erotomania are highlighted. The distinction between idiopathic, primary, and secondary erotomania is discussed. Numerous psychiatric and somatic conditions that can manifest secondary erotomania are described. Considerations are also included in the forensic-psychiatric context, given the potential for legal problems in patients with erotomania.