Cutaneous lupus erythematosus (CLE) is a disease with different subtypes and the new classification system includes acute CLE (ACLE), subacute CLE (SCLE), chronic CLE (CCLE), and intermittent CLE (ICLE). The broad spectrum of skin involvement and the possibility of systemic organ manifestations at the beginning and during the course of CLE require specific diagnostic procedures. Clinical assessment of the cutaneous manifestations is necessary along with a detailed patient's history. The diagnosis of CLE is confirmed by histopathology and immunofluorescence microscopy. Selective laboratory screening and additional diagnostic procedures depending on clinical symptoms are recommended. Photoprovocation tests can be performed to assess photosensitivity in patients with CLE and to support the diagnosis. Recently, a scoring system for the activity of the cutaneous manifestations in CLE has been developed and is now evaluated in several clinical studies. In this review, the classification and the characteristic clinical criteria of the different CLE subtypes as well as the current diagnostic possibilities are emphasized.